Decision-making as discovery: Vetting clinical research in a leading precision oncology service

Based on fieldwork carried out at the Early Drug Development Service of a world-leading cancer institution, our study sheds lights on decision-making processes at the stage where decisions are made about which clinical trial to pursue and thus which experimental drugs will feed the growing pipeline of molecularly guided therapies and therapeutic strategies available to treating physicians. The paper shows how such collective decision-making practices by a translational research unit employ formal tools and ad hoc valuation strategies that interweave technical-scientific matters of concern with patient-oriented clinical ones, as part of the institutional assetization of biomedical knowledge production. In the process, decision-making practices in part define the conditions of possibility for the provision of care in what is increasingly becoming a 'clinic of variants.' They do so by reconfiguring on an evolving basis the socio-material ecosystem through which precision oncology is enacted as a rapidly evolving assemblage of patients, physicians, research and support staff, protocols, molecular markers, drugs and administrative components.

Organizing precision medicine: A case study of Memorial Sloan Kettering Cancer Center's engagement in/with genomics

Recent decades have seen a dramatic rise of in the number of initiatives designed to promote precision oncology, a domain that has played a pioneering role in the implementation of post-genomic approaches and technologies such as innovative clinical trial designs and molecular profiling. In this paper, based on fieldwork carried out at the Memorial Sloan-Kettering Cancer Center from 2019 onwards, we analyze how a world-leading cancer center has adapted, responded, and contributed to the challenge of "doing" precision oncology by developing new programs and services, and building an infrastructure that has created the conditions for genomic practices. We do so by attending to the "organizing" side of precision oncology and to the nexus between these activities and epistemic issues. We situate the work that goes into making results actionable and accessing targeted drugs within the larger process of creating a precision medicine ecosystem that includes purpose-built institutional settings, thus simultaneously experimenting with bioclinical matters and, reflexively, with organizing practices. The constitution and articulation of innovative sociotechnical arrangements at MSK provides a unique case study of the production of a large and complex clinical research ecosystem designed to implement rapidly evolving therapeutic strategies embedded in a renewed and dynamic understanding of cancer biology.

Abstract 3931: BRD4, BRD3, NSD3, and ZNF532 fusions in histologies beyond NUT carcinomas: Investigation of a large pan-cancer cohort

Background: NUT rearrangements drive NUT carcinomas (NCs), which are rare, poorly differentiated tumors with a survival from diagnosis of ~6-7 months. Common NUT fusion partners (NCFPs) include BRD4, BRD3, NSD3, and ZNF532, which are associated with epigenetic changes leading to tumor growth. Recent clinical trials have aimed to address NCs, but little is known about fusions involving NCFPs in other histologies. We characterized NCFPs in a large, pan-cancer cohort.

Methods: The MSK-IMPACT (DNA sequencing; n=71,423) and MSK-Fusion (RNA sequencing; n=10,897) clinical cohorts were mined to identify patients (pts) with all forms of structural variants (SVs) involving NCFPs, detected between April, 2015 and June, 2022. The targeted NGS panels included BRD4 and NSD3 only; detection of BRD3 and ZNF532 SVs was possible for fusions with a partner present on either panel. SVs were manually reviewed to identify in-frame fusions with oncogenic potential if critical domains present in NC fusions were conserved. Pts were followed through July 2022 and manual chart review enabled assessment of treatment history and clinical outcomes.

Results: SVs involving NCFP genes were detected in 182 (BRD4=110, NSD3=61, BRD3=8 and ZNF532=3) pts (0.002%). Putative NCFP fusions not involving any of the NUT gene family members comprised a total of 20 fusions with likely oncogenic potential including 11 with BRD4 (55%), 5 with NSD3 (25%), 3 with ZNF532 (15%), and 1 with BRD3 (5%). BRD4::NOTCH3 and ZNF532::MALT1 were the most enriched fusions, present in 3 samples each. The most common histologies were breast (3 ductal; 1 lobular), lung (2 squamous cell carcinoma, 1 adenocarcinoma and 1 mixed histology), and colon and esophageal adenocarcinoma (2 samples each). Median age at diagnosis was 62. 11 (55%) pts were female and 9 (45%) were male. 13 (65%) pts ultimately were diagnosed with stage IV disease and had a median overall survival from stage IV diagnosis of 2.5 years (95% CI: 1.41, NR). DNA sequencing in 19/20 tumors revealed a mean tumor mutational burden (TMB) of 5.0 mut/Mb including 15 with low TMB (<10) and 3 with high TMB (>10). No tumor showed microsatellite instability (MSI-high). TP53 mutations were the most common co-alteration, found in 11 (58%) cases. 18/20 pts received systemic therapy; 18 (90%) received cytotoxic chemotherapy and/or mAb therapy, including 13 (65%) who received a platinum. 8 pts (40%) received immunotherapy (IO), and 4 (20%) received small molecule inhibitors. No pts received BET inhibitors. Among pts who received IO, median time to treatment discontinuation was 64 days (95% CI: 20, NR).

Conclusion: Tumor sequencing from a large cohort reveals potential oncogenic fusions involving BRD4, BRD3, NSD3, and ZNF532 across multiple histologies. Further biological characterization of their oncogenicity and potential targetability is warranted.

Citation Format: Ian R. Nykaza, Christopher A. Febres-Aldana, Sabrina T. Lin, Ryma Benayed, Kerry Mullaney, Emiliano Cocco, Alexia Iasonos, Marc Ladanyi, Alexander E. Drilon, Yonina R. Murciano-Goroff. BRD4, BRD3, NSD3, and ZNF532 fusions in histologies beyond NUT carcinomas: Investigation of a large pan-cancer cohort. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3931.

Abstract 1394: Comprehensive clinical and genomic analysis for patients with MYC, MYCN, and MYCL amplified solid tumors

Introduction: The MYC gene family (MYCf), which includes MYC, MYCN, and MYCL, is deregulated in ~70% of cancers and is associated with treatment resistance. Whereas older investigational therapies for MYC amplified tumors were unsuccessful, promising novel targeted therapies are in early phase clinical trials. Unfortunately, it remains unclear how to select patients whose cancers may harbor true MYC addiction. We thus sought to characterize factors such as amplification level, focality, and clonality that may correlate with increased MYC dependence.

Methods: Utilizing a center-wide next generation sequencing (NGS) program of >71,000 sequenced patients, genomic and clinical data from pediatric and adult patients with MYC, MYCN, and MYCL amplifications were identified between 2014 and 2022. Patients were characterized as harboring MYC, MYCN, and MYCL amplification based on a read-depth methodology using a DNA-based hybrid-capture NGS (MSK-IMPACT) and Fraction and Allele-Specific Copy Number Estimates from the Tumor Sequencing (FACETS). All cases underwent clinical data curation including baseline demographic, tumor characteristics, and treatment histories.

Results: We identified 3911 cancers with MYCf amplification (n=3257 (82%) MYC; n=364 (9%) MYCL; n=330 (8%) MYCN) across 40 malignancies, for an overall 5.5% incidence. The most frequent tumor types with MYCf amplification were breast (22%), non-small cell lung (NSCLC) (11%), colorectal (8%), ovarian (8%), prostate (7%), brain (5%), and small cell lung cancers (SCLC) (2%). Cancers with MYC amplification had longer segment lengths than MYCL and MYCN amplification, which appeared more focal (median = 19, 4.3 and 4.5 MB, respectively, p < 0.001). MYCN amplified cancers had higher total copy number than MYC and MYCL amplified cancers (median = 19, 8, 9, respectively, p < 0.001). MYC, MYCN, and MYCL samples were predominantly clonal (median clonal fraction > 99% for all genes). Most NSCLC, squamous cell lung cancers, and pulmonary carcinoids had MYC amplifications (93%, 70%, and 67% respectively). Conversely, SCLCs most often had MYCL amplifications (49%). No concurrent targetable driver alterations were found in 33% of metastatic NSCLCs with MYC, 75% of MYCN, and 6% of MYCL amplifications.

Conclusions: While MYCf amplification is observed across a broad range of cancer types, factors such as gene type (MYC, MYCN, MYCL), focality, total copy number, clonality, and concurrent oncogenic drivers vary widely. Novel MYC-directed trials may consider enrichment for a subpopulation of cancers with higher-level, focal, and clonal MYCf amplifications without concurrent other drivers.

Citation Format: Monica F. Chen, Allison Richards, Patrick Evans, Patrick Lee, Adam Price, Matteo Repetto, Soo Ryum Yang, Jason Chang, Rose Brannon, Ezra Rosen, David Brown, Charles Rudin, Nitya Raj, Mark G. Kris, Jorge Reis-Filho, Mark Donoghue, Alexander E. Drilon, Noura J. Choudhury. Comprehensive clinical and genomic analysis for patients with MYC, MYCN, and MYCL amplified solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1394.

Tumor agnostic efficacy of selpercatinib in patients with RET fusion+ solid tumors: A global, multicenter, registrational trial update (LIBRETTO-001)

3094

Background: Selpercatinib, a first-in-class highly selective and potent RET kinase inhibitor, is approved in multiple countries for the treatment of lung and thyroid cancer with RET fusions and medullary thyroid cancer with RET mutations. We provide an efficacy and safety update with more patients (pts) and longer follow-up (data cut-off: 24Sep2021) in RET fusion+ solid tumors with histologies other than lung/thyroid. Methods: The phase 1/2 LIBRETTO-001 trial (NCT03157128) enrolled pts with locally advanced/metastatic RET fusion+ solid tumors. Following dose escalation, pts received the recommended dose of 160 mg orally twice daily. The efficacy analysis set consisted of pts enrolled ≥6 months (mo) prior to the cut-off date. If a pt achieved response, an additional ≥6 mo follow-up from the initial response was required. There was no additional follow-up required for non-responders. Response was assessed per RECIST 1.1. Primary endpoint was objective response rate (ORR) by independent review committee (IRC). Secondary endpoints included ORR by investigator (INV), duration of response (DoR), progression-free survival (PFS), time to response (TTR), and safety. Results: Forty-five pts with 14 unique RET fusion+ tumor types received ≥1 dose of selpercatinib: 12 pancreatic, 10 colon, 4 salivary, 3 unknown primary, 3 sarcoma, 2 each of breast, carcinoma of the skin, xanthogranuloma, and cholangiocarcinoma, and 1 each of lung carcinoid, rectal neuroendocrine, small intestine, ovarian, and pulmonary carcinosarcoma. Median age was 53 years (range 21-85). Forty-one pts received prior systemic therapy (median prior lines: 2, range 0-9); 31% received ≥3 lines. In 41 efficacy-evaluable pts, confirmed ORR by IRC was 44% (18/41, 95% CI: 29-60). Clinical benefit was observed in 63% (26/41) of pts: 2 complete responses (breast, small intestine), 16 partial responses, and stable disease ≥16 weeks in 8 pts by IRC. Responses were observed across a variety of fusion partners. Median TTR was 1.9 mo by IRC. Median DoR was 24.5 mo (95% CI: 9.2-NE) with 50% (9/18) of responses ongoing at a median follow-up of 14.9 mo by IRC. Median PFS by IRC was 13.2 mo (95% CI: 7.4-26.2), with 34.1% alive and progression-free at a median follow-up of 16.4 mo. No new safety signals were identified in this cohort compared to broader safety database. Three grade 5 AEs were observed (unrelated to treatment by INV), and 4 pts discontinued treatment due to AEs (1 deemed related to treatment by INV). Conclusions: Selpercatinib continued to demonstrate durable antitumor activity in pts with RET fusion+ cancers across multiple tumor types. No new safety signals were identified. These results emphasize the importance of comprehensive genomic profiling to identify actionable oncogenic drivers, including RET fusions. The LIBRETTO-001 study continues to enroll pts. Clinical trial information: NCT03157128.

CRESTONE: Initial efficacy and safety of seribantumab in solid tumors harboring NRG1 fusions

3006

Background: NRG1 fusions are rare oncogenic drivers found in ̃0.2% of all solid tumors. These fusions elicit ERBB3/HER3 overactivation to drive tumor growth and cancer cell survival. Currently there are no approved targeted therapies for NRG1 fusion-positive tumors. Furthermore, patients (pts) with tumors harboring NRG1 fusions have poor outcomes with standard therapies. Seribantumab is a fully human anti-HER3 IgG2 monoclonal antibody that suppressed tumor growth in NRG1 fusion-driven preclinical models. Here, we present initial clinical data from the CRESTONE study (NCT04383210). Methods: CRESTONE is a Phase 2, global, multicenter, open-label study of seribantumab in adult pts with locally advanced or metastatic solid tumors harboring NRG1 fusions. A dose ranging phase established the RP2D as a 3g once weekly (QW) intravenous dose administered until treatment discontinuation criteria are met. In the expansion phase, cohort 1 will enroll at least 55 pts who had received at least one prior therapy and are naïve to ERBB-targeted therapy. Exploratory cohorts 2 or 3 will enroll pts previously treated with ERBB-targeted therapies and/or tumors harboring additional molecular alterations. The primary endpoint is objective response rate (ORR) by independent central review per RECIST v1.1. Initial data from cohort 1 pts who received seribantumab 3g QW with investigator (INV)-assessed response per RECIST v1.1 are reported. Results: By JAN-13-2022, 12 pts have received seribantumab 3g QW in cohort 1. Median age was 65 years (range 44–76), 67% were female, and median number of prior therapies was 1 (range 1–5). 92% (11/12) of pts had non-small cell lung cancer (NSCLC); 5 different NRG1 fusion partners ( ATP1B1, CD74, ITG B1, SDC4, SLC3 A2) were reported by local next-generation sequencing tests. Among 10 pts evaluable for INV-assessed response, the confirmed ORR was 30%, and the disease control rate was 90% (1 complete response, 2 partial responses, 6 stable disease, 1 progressive disease). 58% (7/12) of pts remain on study treatment, including 2 pts with NSCLC who achieved objective responses with an ongoing duration of response of 6 and 8.5 months. Seribantumab 3g QW was well tolerated with no drug discontinuations or dose reductions. Across all cohorts (n = 29), the most frequently (≥20%) reported treatment-related adverse events (TRAEs) were diarrhea (38%), fatigue (34%), and rash (24%), all were grade 1 or 2. One grade 3 TRAE of vomiting occurred; there were no Grade 4 or 5 TRAEs. Efficacy analysis is ongoing and updated efficacy data from evaluable pts in cohort 1 will be presented. Conclusions: Initial data indicate seribantumab induced durable responses in advanced solid tumors harboring NRG1 fusions and has a favorable safety profile. These data support the continued evaluation of seribantumab in NRG1 fusion-positive solid tumors in the ongoing CRESTONE study. Clinical trial information: NCT04383210.

Central nervous system (CNS) outcomes and progression patterns in patients with RET fusion-positive lung cancers treated with selpercatinib

3109

Background: Selpercatinib, a potent/selective RET inhibitor, is approved for the treatment of RET fusion-positive non-small cell lung cancers. While the drug is known to have substantial intracranial activity (intracranial ORR 82%) in patients with existing brain metastases, (1) central nervous system (CNS) outcomes in patients without brain metastases and (2) CNS progression patterns in patients with brain metastases have not been explored. Methods: Patients with advanced RET fusion-positive lung cancers were prospectively treated with selpercatinib on the registrational LIBRETTO-001 trial (NCT03157128) or the LIBRETTO-201 multi-center expanded access program (EAP, NCT03906331). Key overall and CNS eligibility criteria were previously presented. Patients with and without pre-selpercatinib brain metastases who underwent serial CNS and extracranial imaging were eligible for analysis. The data cutoff was November 24, 2020. Cumulative incidence rates (CIRs) were calculated using a competing risk model with systemic progression of disease (PD) or death as competing risks; patients with simultaneous CNS and systemic PD were treated as having had CNS PD. Results: Sixty-two patients (48 LIBRETTO-001, 14 EAP) were identified. Median age was 64. Thirty-two (52%) were female and 47 (76%) were never smokers. The most common 5’ fusion partner was KIF5B (68%). The median number of prior therapies was 2 (range 1-11); 34% received prior multikinase inhibitor therapy. The median time on treatment was 21.8 months. Thirty-one (50%) patients had no baseline brain metastases. In these patients, the CIR of CNS metastasis was 0% at 6 months and 12 months; none of these patients developed CNS metastasis during selpercatinib treatment. The 9 patients that progressed did so extracranially. Of the 31 patients with baseline brain metastases, 12 (39%) had prior CNS radiation and 3 (10%) had prior CNS surgery. At the time of data cut-off, 23 patients had some evidence of progression, including 8 in both the CNS and systemically, 6 only in the CNS, and 9 only systemically. Overall, 17 of the 31 patients with baseline brain metastasis did not develop evidence of CNS progression as of the data cut. Among patients with baseline brain metastasis, the CIR for evidence of CNS PD was 6.7% at 6 months and 27.4% at 12 months. Conclusions: In patients with RET fusion-positive lung cancers without baseline brain metastases, new CNS metastases were not observed during selpercatinib therapy. Among patients with baseline brain metastasis, a substantial number did not experience progression in the CNS on treatment.

LIBRETTO-001 cohort 7: A single-arm, phase 2 study of neoadjuvant selpercatinib in patients with resectable stage IB-IIIA RET fusion-positive NSCLC

TPS8594

Background: Despite definitive surgery and perioperative chemotherapy, many patients with locoregional non-small cell lung cancer (NSCLC) continue to experience recurrent disease and limited survival. Although targeted therapies are standard treatment for metastatic NSCLC with genomic alterations, their use in the early-stage setting is still being characterized. Initial studies examining targeted therapy in neoadjuvant setting for early-stage epidermal growth factor receptor positive NSCLC has shown promise. Selpercatinib is a highly selective, potent, and central nervous system active rearranged during transfection (RET) inhibitor with demonstrated robust and sustained antitumor activity and manageable toxicity in patients with RET fusion-positive advanced NSCLC. Cohort 7 of the Phase 2, open-label, single arm LIBRETTO-001 study evaluates efficacy and safety of neoadjuvant selpercatinib in patients with resectable stage IB-IIIA RET fusion-positive NSCLC (NCT03157128). Methods: Key eligibility criteria include age ≥18 years; histologically confirmed stage IB–IIIA NSCLC (AJCC, version 8); presence of RET fusion in tumor (by PCR or NGS) or blood (by NGS) (pre-treatment biopsy confirmed); resectable and operable tumor; measurable disease (RECIST 1.1); and ECOG performance status 0-1. Key exclusion criteria include presence of other known oncogenic drivers; and concurrent investigational anticancer therapy. Eligible patients will undergo full staging including radiographic tumor measurements using CT, PET, and brain MRI at baseline and after two 28-day cycles of neoadjuvant selpercatinib, followed by surgery. Dosing regimen is 160 mg twice daily. Resected tumor specimens will be sent to an Independent Pathology Review Committee (IPRC) for evaluation. Patients may then be treated with stage-appropriate adjuvant therapy/surveillance, based on the treating physician’s decision, followed by selpercatinib until disease recurrence, unacceptable toxicity, withdrawal, or death, for a maximum treatment duration of 3 years. The primary endpoint is to determine the rate of major pathologic response (MPR) by IPRC, defined as ≤ 10% residual viable tumor cells in the surgically resected specimen. Efficacy based on the MPR will be assessed using the Simon's 2-stage design. In Stage I, 9 patients will be enrolled; if ≤1 patient achieves an MPR, the study will be stopped. Otherwise, at least 10 additional patients will be enrolled, with a total of 19 patients undergoing surgery. The rate of pathologic complete response (pCR) by IPRC, disease-free survival, and overall survival will be assessed as secondary endpoints. pCR rate will be determined at the time of surgery, indicating no remaining viable tumor cells. Safety of peri-operative treatment will be assessed, including 30- and 90-day post-operative readmission and mortality rates. Clinical trial information: NCT03157128.

A first-in-human phase 1 study of the next-generation RET inhibitor, LOXO-260, in RET inhibitor refractory patients with RET-altered cancers (trial in progress)

TPS8595

Background: RET fusions are found in 1-2% of lung adenocarcinomas and 10-20% of papillary thyroid carcinomas. Activating RET mutations occur in 50-60% of medullary thyroid cancers (MTCs). Selpercatinib was the first selective RET inhibitor approved by the FDA and is indicated for patients (pts) with RET fusion-positive NSCLC and thyroid cancer, and RET mutant MTC. Despite marked and durable activity, acquired resistance can eventually develop through a variety of mechanisms. These include acquisition of RET G810X mutations at the solvent front of the ATP pocket. LOXO-260 is a highly potent and selective inhibitor of RET designed to have activity against both solvent front and gatekeeper mutations, expressed alone or together, while maintaining potency against RET fusions or mutations (Kolakowski GR. et al. 2021 Cancer Research 81 (13 Suppl) 1464). Methods: LOXO-NGR-21001 is a global, open-label, first-in-human phase 1 study of LOXO-260 in pts with RET fusion-positive advanced solid tumors and RET mutant MTC who received a prior selective RET inhibitor. Phase 1a dose escalation will utilize a modified i3+3 design, allowing for pt backfill to previously cleared dose levels. Phase 1b dose expansion will evaluate LOXO-260 in specific expansion cohorts: RET fusion-positive NSCLC or thyroid cancers and RET mutant MTC. The primary objectives in dose escalation are to determine the MTD/RP2D and safety of LOXO-260. Key secondary objectives include characterization of PK and preliminary antitumor activity of LOXO-260 per RECIST v1.1. The primary objective of dose expansion is to assess the antitumor activity of LOXO-260 based on investigator-assessed overall response rate (ORR). Key secondary objectives are to characterize the PK and antitumor activity of LOXO-260 based on progression-free survival (PFS), time to response (TTR), and duration of response (DOR). Eligible pts must have received a prior selective RET inhibitor, have a documented RET fusion or RET mutation and a diagnosis of locally advanced, unresectable and/or metastatic cancer per disease-specific criteria, and must have progressed or be intolerant to standard therapies or must have refused such a therapy. Pts must be ≥18 years old and have an ECOG PS of 0-2. Key exclusion criteria include presence of serious cardiac conditions, interstitial lung disease, symptomatic CNS metastases, or carcinomatous meningitis. Clinical trial information: NCT05241834.

Clinicopathologic and mutational landscape of BRAFV600E-mutant non–small cell lung carcinoma

9084

Background: BRAF mutations (mts) occur in 2-5% of non-small cell lung cancers (NSCLC) with approximately 50% being BRAFV600E. Limited data is known regarding the mutational landscape (ML) and prognostic role of co-mutations in BRAFV600E NSCLC. We performed this study to evaluate clinicopathological characteristics and the impact of ML in BRAFV600E NSCLC. Methods: Patients (pts) with BRAFV600Emutant NSCLC were identified using MSK-IMPACT at Memorial Sloan Kettering Cancer Center between January 2014 to October 2021. Baseline clinicopathological characteristics and treatment outcomes were annotated. Due to the enrichment of SETD2 in BRAFV600E NSCLC, we conducted further analyses using cbioportal to identify co-mutations of SETD2 with other actionable mutations in NSCLC. Overall survival (OS) was assessed from the date of metastatic disease until death using the log-rank test. Results: BRAF mutations were detected in 5% of NSCLC samples (512/10220) with 22% (97/435 pts) being BRAFV600E. Of the 97 pts with BRAFV600E NSCLC identified: 57 pts (59%) were females, median age of 68 (range: 38-93 years), 58 pts (60%) were former smokers. All BRAFV600E tumors were adenocarcinoma and the median tumor mutational burden was 5 mt/Mb (range: 0-40). 46 pts (48%) with BRAFV600E NSCLC were diagnosed with de novo metastatic disease. Pts receiving targeted therapy at first, second, and subsequent lines of therapy numbered 17 (29%), 18 (31%), and 10 (17%) respectively. Co-alterations of BRAFV600E with TP53 and SETD2 were found in 45% (44/97) and 42% (41/97), respectively. There is a much lower prevalence of concurrent inactivating SETD2 mutations than with other actionable alterations in NSCLC: ROS1 (9%), ALK (8%), RET (8%), HER2 (6%), MET (5%), KRAS (5%), EGFR (2.9%) and BRAFnon-V600E (2%). Median OS in BRAFV600E+/ TP53+ vs BRAFV600E+/ SETD2+ were 35 vs 36 mos (HR 0.88m 95% CI 0.45-1.75, P= 0.71) and BRAFV600E+/ TP53+/ SETD2+ vs BRAFV600E+/ TP53-/ SETD2- were 19 vs 39 mos (HR 0.37, 95% CI 0.09-1.50, P= 0.06). Conclusions: Among the BRAFV600E lung adenocarcinomas, concurrent TP53 mutation and SETD2 inactivation define a patient subset with significantly shorter overall survival. Further studies are warranted to investigate the role of SETD2 mutations in the context of BRAFV600E in NSCLC pts.

A phase 1/2 study of REGN5093-M114, a METxMET antibody-drug conjugate, in patients with mesenchymal epithelial transition factor (MET)-overexpressing NSCLC

TPS8593

Background: MET, also called hepatocyte growth factor receptor (HGFR), is a high-affinity transmembrane protein receptor for HGF. MET is overexpressed in various malignancies, including non-small cell lung cancer (NSCLC). MET overexpression can accompany MET exon 14 alteration or de novo/acquired MET amplification. REGN5093-M114 is an antibody drug conjugate composed of a novel linker-payload (M114, carrying the maytansine derivative M24, a potent inhibitor of microtubule assembly) covalently bound to lysine residues on a MET-targeting human IgG4p bispecific antibody, REGN5093. In preclinical models of MET overexpressing cancers, REGN5093-M114 demonstrated significant dose-dependent antitumor activity. Methods: This is an open label, phase 1/2, first-in-human, multicenter dose-escalation study with cohort expansion evaluating REGN5093-M114 in patients with MET-overexpressing NSCLC (NCT04982224). Patients must have advanced stage NSCLC for which there are no approved therapies available expected to confer clinical benefit, with tumor overexpressing MET (≥75% tumor cell staining at 2+) as centrally confirmed by immunohistochemistry. For the expansion phase, patients must have at least one lesion that is measurable by RECIST 1.1. REGN5093-M114 will be administered intravenously once every 3 weeks over 30 minutes until disease progression, intolerable adverse events, withdrawal of consent, or study withdrawal. The primary objectives in dose escalation are to evaluate safety, tolerability, PK, and maximum tolerated dose and/or recommended phase 2 dosing regimen of REGN5093-M114. PKs will include the assessment of REGN5093-M114, total antibody, and payload M24 concentrations. The primary objective in dose expansion is to assess preliminary anti-tumor activity of REGN5093-M114 in MET-overexpressing NSCLC as measured by the objective response rate. The secondary objectives of both phases of the study include an evaluation of treatment durability, and the immunogenicity of REGN5093-M114. This study is currently open to enrollment. Clinical trial information: NCT04982224.

Chylothorax and chylous ascites during RET tyrosine kinase inhibitor therapy

9080

Background: Spontaneous, atraumatic chylous effusions are rare. Investigators have observed a higher than anticipated incidence of chylothorax and chylous ascites in patients (pts) treated with RET tyrosine kinase inhibitors (TKIs). A systematic analysis of the occurrence of chylous effusions during RET TKI therapy and management strategies was thus performed. Methods: In this multicenter, retrospective study, the frequency of biochemically confirmed chylothorax or chylous ascites in pts treated with multikinase inhibitors (MKIs) with anti-RET activity or selective RET TKIs was determined. Clinicopathologic features and management of pts with chylous effusions were assessed. Results: A pan-cancer cohort of 7517 pts treated with at least 1 of 17 MKIs and selective RET TKIs and an independent cohort of 96 pts treated with the selective RET TKIs, selpercatinib or pralsetinib, were identified. Across cohorts, chylous effusions were identified in 22 pts and were most common with selpercatinib (7%; 15/217), followed by the MKIs agerafenib (4%; 1/24), cabozantinib (0.3%; 3/918), and lenvatinib (0.3%; 3/1185). Chylous effusions were not noted in 28 pts treated with pralsetinib. The distribution of malignancies included lung adenocarcinoma (54%) medullary thyroid carcinoma (23%), renal cell carcinoma (19%), and desmoplastic small round cell tumor (4%). Of the 22 pts, 12 had chylothorax, 5 had chylous ascites, and 5 had both. The cumulative incidence of chylous effusions from TKI initiation at 12 months was 3.09%. Median fluid triglyceride level was lower in chylothorax than in chylous ascites [397 mg/dL (IQR 282-4000) vs. 3786 mg/dL (IQR 676-6596), p = 0.035]. Median pleural fluid triglyceride level was higher with selpercatinib compared to MKIs [4,000 mg/dL (IQR 356-4425) vs. 287 mg/dL (IQR 216-395); p = 0.017]. Malignant cells were identified in the effusions from 12% (2/17) and 10% (1/10) of pts with chylothoraces and chylous ascites, respectively. Median time to disease progression from radiographic index and biochemical index across the full cohort was 1.5 years (IQR: 0.6-2.4) and 1.0 year (IQR: 0.1-1.2), respectively. Anatomic chyle leak was not identified in 6 pts who underwent lymphangiography. After initial drainage, additional drainage procedures were required in all cases with chylothorax and 50% of cases with chylous ascites. Chylous effusions prompted TKI dose reduction in 47% (7/15) of pts treated with selpercatinib and 14% (1/7) treated with MKI; none discontinued TKI due to chylous effusions. Conclusions: Chylous effusions can emerge on treatment with certain MKIs or selective RET TKIs. Recognition of this potential side effect is key to prevent misattribution of worsening effusions to progressive malignancy and to motivate a better understanding of its biology and management.

Long-term control and safety of larotrectinib in a cohort of adult and pediatric patients with tropomyosin receptor kinase (TRK) fusion primary central nervous system (CNS) tumors

2010

Background: Neurotrophic tyrosine receptor kinase ( NTRK) gene fusions are known oncogenic drivers in a variety of tumor types. Larotrectinib is a highly selective, CNS-active TRK inhibitor that demonstrated an objective response rate (ORR) of 30% and a 24-week disease control rate (DCR) of 73% across 33 evaluable adult and pediatric patients with TRK fusion primary CNS tumors, as of July 2020 (Doz et al, Neuro Oncol 2021). We report updated data on an expanded dataset of patients. Methods: Patients with TRK fusion primary CNS tumors in two clinical trials (NCT02637687, NCT02576431) were included. Larotrectinib was administered at 100 mg twice daily (BID) in adults and 100 mg/m2 (max 100 mg) BID in pediatric patients. Response was investigator-assessed. Results: As of July 2021, 38 adult and pediatric patients with TRK fusion primary CNS tumors were identified: high-grade glioma (HGG; n =23), low-grade glioma (LGG; n =9), and other (n =6; includes glioneuronal, neuroepithelial, diffuse leptomeningeal, neuroblastoma, recurrent small round blue cell, and not otherwise specified). Median age at enrollment was 10.8 years (range 1.3–79.0; 28 [74%] patients < 18 years old). The gene fusions involved NTRK2 (n = 28), NTRK1 (n = 6), and NTRK3 (n = 4). Sixteen (42%) patients received one prior line of systemic therapy and 16 (42%) received ≥2 prior lines. The ORR for 37 evaluable patients was 30% (95% confidence interval [CI] 16–47): three complete responses, eight partial responses, 21 stable disease (16 patients ≥24 weeks), and five progressive disease. The 24-week DCR was 73% (95% CI 56–86) for all patients, 68% (95% CI 45–86) for patients with HGG, and 89% (95% CI 52–100) for patients with LGG. Twenty-five of 31 patients (81%) with measurable disease at baseline had tumor shrinkage. Median time to response was 1.9 months. Median duration of response (DoR) was not reached; median follow-up was 25.6 months. The 12-month DoR rate was 64%. Median progression-free survival (PFS) was 16.5 months (95% CI 6.7–not estimable); median follow-up was 27.4 months. Median overall survival (OS) was not reached; median follow-up was 26.7 months. The 24-month OS rate was 65%. Treatment duration ranged from 0.1+ to 38.7+ months. Twenty-two patients (58%) progressed on treatment and three continued treatment post-progression for ≥4 weeks. Treatment-related adverse events (TRAEs) were reported in 21 patients (55%); the majority of these patients (18/21 [86%]) reported Grade 1 or 2 TRAEs. No Grade 3 or higher treatment-related neurological adverse events were reported. There were no treatment discontinuations due to TRAEs. Conclusions: Larotrectinib achieved a high DCR, rapid and durable responses, and a manageable safety profile in patients with TRK fusion primary CNS tumors. These results support testing for NTRK gene fusions in patients with CNS tumors. Clinical trial information: NCT02637687, NCT02576431.

Efficacy and safety of zenocutuzumab, a HER2 x HER3 bispecific antibody, across advanced NRG1 fusion (NRG1+) cancers

105

Background: NRG1 fusions are rare oncogenic drivers that have been identified in a variety of solid tumors. These proteins bind HER3, leading to HER2/HER3 heterodimerization and oncogenic transformation. Zenocutuzumab (MCLA-128; Zeno) is a Biclonics antibody that overcomes HER3 mediated NRG1 (or NRG1 fusion) signaling in tumor cells. Zeno docks on HER2, then binds to and blocks the NRG1 fusion-HER3 interaction and HER3 heterodimerization with HER2. Zeno is being evaluated in patients (pts) with NRG1+ cancer in the ongoing pivotal phase 2 part of the eNRGy study and early access program (EAP). Methods: Pts with NRG1 + solid tumors previously treated with or not candidates for standard therapy, aged ≥ 18 years, with ECOG PS ≤ 2, and measurable (RECIST 1.1) or evaluable disease, were enrolled. NRG1 fusions were determined by next generation sequencing (NGS) before enrollment. Zeno (750 mg IV Q2W) was administered until disease progression or unacceptable toxicity. Tumor imaging was conducted every 8 weeks. The primary endpoint is investigator (INV)-assessed objective response rate (ORR) and secondary endpoints include duration of response (DOR) and safety. Results: As of 12 Jan 2022, 99 pts with NRG1 + cancer (85 eNRGy, 14 EAP) were enrolled. Efficacy was assessed in 73 pts who received ≥ 1 dose of Zeno and who were enrolled as of 12 Jul 2021 to allow for the opportunity to have ≥ 6 months (mo) follow-up and met the criteria for the primary efficacy population. Median age was 59 y (range 22–84), 58% were female, 47%/53% pts had ECOG PS 0/1. Tumor types were non-small cell lung cancer (NSCLC; 41 pts), pancreas cancer (18 pts), breast cancer (5 pts), cholangiocarcinoma (3 pts), colorectal cancer (2 pts), and 4 other tumor types (1 pt each), with a median 2 prior systemic therapies (range 0-9). The most frequent fusion partners were CD74 (27%), SLC3A2 (18%), and ATP1B1 (15%). Among the 71 pts with measurable disease, the INV-assessed confirmed ORR was 34% (90% CI, 25;44), including responses in NSCLC (35%; 14/40 pts), pancreas cancer (39%; 7/18 pts), breast cancer (2/4 pts), and cholangiocarcinoma (1/3 pts). Responses occurred at the first tumor assessment in 20/24 responders, and are ongoing in 13 pts. Treatment is ongoing in 22 pts (13 NSCLC, 6 pancreas, 3 other solid tumors). Median DOR was 9.1 mo (95% CI, 5.2-12.0). Kaplan-Meier estimate of DOR rate at 6 mo was 70%. Among the 208 pts treated with Zeno monotherapy across all dosing schedules in the phase 2 setting, for individual adverse events irrespective of causality, grade ≥ 3 events were reported in <5% of pts. Conclusions: Zeno demonstrated robust and durable efficacy in pts with advanced NRG1+ cancer regardless of tumor histology. A well tolerated safety profile of Zeno was observed. Clinical trial information: NCT02912949.

Clinicopathologic characterization of ERK2 E322K mutation in solid tumors: Implications for treatment and drug development

3135

Background: MAPK1 encodes ERK2, a kinase component of the mitogen activated signaling (MAPK) pathway. ERK2 E322K is a known activating mutation that leads to increased phosphorylation and ERK signaling. In vitro studies found this mutation to be associated with resistance to dabrafenib, trametinib, but potential sensitivity to ERK inhibitors. Despite its potential as a drug target, little is known about the clinicopathologic characteristics of this hotspot mutation across solid tumors. Methods: Patients with solid tumors underwent tumor next-generation sequencing at Memorial Sloan Kettering Cancer Center between Jan 2015 and Sep 2020 using the MSK-IMPACT assay. Using the cBioPortal database and clinical charts, we analyzed tumors harboring MAPK1/ERK2 E322K mutations, assessed their clinicopathologic characteristics, co-mutational status and overall survival (OS). OS was measured from time of tumor sequencing to date of death or last follow-up. Results: A total of 37 tumor samples from 35 patients were identified in 59,822 tumors sequenced (0.06%) to harbor an ERK2 E322K mutation. The distribution across tumor types was as follows: head and neck squamous cell carcinoma (29%), bladder cancer (20%), lymphomas (9%), colorectal cancers (9%), gastric cancers (9%), cholangiocarcinoma (6%), cervical cancers (6%), lung cancers (6%), germ cell tumor (3%), Merkel cell carcinoma (3%), and breast cancers (3%). The OS in patients with metastatic disease and ERK2 E322K was 22.29 months (95%CI: 7.56-NA) months. Other mutations in RAS pathway frequently co-occurred with ERK2 E322K mutation (17/37, 46%). Concurrent mutations are also involved in pathways of cell cycle (71%), PI3K (71%), TP53 (66%), NOTCH (57%), RTK (51%), HIPPO (29%), TGF-beta (29%), WNT (26%), NRF2 (20%), MYC (14%). The median TMB score of samples from solid malignancies was 12.3 (range:0-101, quartiles: 6.9-33.0) mutation/Mb. Two patients (2/35, 6%) had microsatellite-instability high (MSI-H) tumors. The most frequent concurrent activating mutations include ARID1A (29%), FBXW7 (26%), PI3KCA (22%), PI3KR1/2/3 (20%), CDKN2A (11%), PTEN (8%), BRCA1/2(8%), FGFR3 (8%), BRAF (6%), Only one of these 35 patients received treatment targeting BRAF/MEK/ERK pathway and achieved partial response. One patient with NSCLC harboring a concurrent EGFR L858R mutation did not respond to erlotinib. One patient with PI3KCA mutated head and neck cancer did not respond to PI3K inhibitor. Two patients had TMB score of 100.9 and 12.9 mutation/Mb had partial response to pembrolizumab. Conclusions: ERK2 E322K mutation is a rare oncogenic mutation across diverse solid tumor types, associated with a high co-occurrence of other activating mutations and a high TMB. The lack of response to other targeted therapies suggests ERK2 E322K is a potential driver mutation. These findings may inform treatment and further development of ERK inhibitors.

Long-term efficacy and safety of larotrectinib in a pooled analysis of patients with tropomyosin receptor kinase (TRK) fusion cancer

3100

Background: Neurotrophic tyrosine receptor kinase ( NTRK) gene fusions are oncogenic drivers in multiple tumors. Larotrectinib is a highly selective, central nervous system (CNS)-active tropomyosin receptor kinase (TRK) inhibitor, approved to treat adult and pediatric patients (pts) with TRK fusion cancer. In an integrated analysis of 206 pts with non-primary CNS TRK fusion cancer, larotrectinib demonstrated an investigator-assessed objective response rate (ORR) of 75%; median progression-free survival (PFS) was 35.4 months (mo; Hong et al, ASCO 2021). We report updated efficacy and safety data based on central review assessments in an expanded dataset. Methods: Data were pooled from three clinical trials (NCT02576431, NCT02122913, and NCT02637687) of pts with non-primary CNS TRK fusion cancer treated with larotrectinib. Larotrectinib was administered until disease progression, withdrawal, or unacceptable toxicity. ORR was assessed by independent review committee (IRC) per RECIST v1.1. Data cut-off was July 20, 2021. Results: As of data cut-off, 244 of 269 larotrectinib-treated pts were evaluable for efficacy by IRC. There were 25 different tumor types. The most common were soft tissue sarcoma (STS [43%], including infantile fibrosarcoma [18%] and other STS [25%]), thyroid (11%), lung (10%), salivary gland (9%), and colorectal (7% [colon, n = 18; rectal, n = 1]). Ninety-four (35%) pts were aged < 18 years; 175 (65%) were ≥18 years. Pts had gene fusions involving NTRK1 (46%), NTRK2 (3%), or NTRK3 (51%). A total of 27%, 28%, and 45% of pts had 0, 1, and ≥2 prior lines of systemic therapy, respectively. The ORR was 69% (95% confidence interval [CI] 63–75): 64 (26%) complete response (CR), including 13 (5%) pathological CR, 104 (43%) partial response,41 (17%) stable disease, 20 (8%) progressive disease, and 15 (6%) not determined. Median time to response was 1.8 mo (range 0.9–16.2). Median duration of response (DoR) was 32.9 mo (95% CI 27.3–41.7); median follow-up was 28.3 mo. Median PFS was 29.4 mo (95% CI 19.3–34.3); median follow-up was 29.3 mo. At a median follow-up of 32.2 mo, median overall survival (OS) was not reached; the 48-mo OS rate was 64% (95% CI 55–73). Treatment duration ranged from 0.1 to 67.9 months. Treatment-related adverse events (TRAEs) were mainly Grade 1–2; 50 (20%) pts had Grade 3–4 TRAEs. Five (2%) pts discontinued treatment due to TRAEs. To exclude the possible confounding effect of ongoing enrollment on median DoR, we conducted an exploratory analysis in the subset of 164 pts who were analyzed as of July 2019. The ORR was 74% (95% CI 67–81) and median DoR was 34.5 mo (95% CI 27.6–43.3); median follow-up was 34.1 mo. Conclusions: With longer follow-up, larotrectinib continued to demonstrate rapid and durable responses, extended survival benefit, and a favorable safety profile. These results highlight the importance of testing for NTRK gene fusions in cancer pts. Clinical trial information: NCT02576431, NCT02122913, NCT02637687.

Mechanisms of acquired resistance to TRK inhibitors

3104

Background: First-generation TRK tyrosine kinase inhibitors (TKIs) are approved in a tumor-agnostic fashion in more than 40 countries for patients with NTRK fusion-positive adult and pediatric cancers. While resistance to these agents has previously been described, the exact frequency with which major mechanisms of resistance emerges is not clearly understood. Methods: Patients with an NTRK-fusion-positive tumor who received a first-generation TRK TKI were eligible. We retrospectively identified those patients that had post-progression tumor tissue analyzed by next-generation sequencing (NGS). The pattern of serial resistance to a second-generation TKI was analyzed when available. Results: Eighteen patients were identified. The median age was 46 years (range 2-67). Nine unique fusions were detected in ten different tumor types. NTRK1, NTRK2, and NTRK3 fusions were found in eight (44%), one (6%), and nine (50%) patients, respectively. Thirteen patients (72%) were treated with larotrectinib and five patients (28%) received entrectinib. NGS (MSK-IMPACT n = 17, Foundation One n = 1) carried out on post-progression tissue revealed the following profile of acquired resistance: on-target resistance (83%, n = 15/18), off-target resistance (11%, n = 2/18), and no identifiable mechanism (6%, n = 1/18). Among patients with on-target resistance, the most common mutation involved the solvent front (87%, n = 13/15: n = 7 NTRK3 G623R, n = 4 NTRK1 G595R, n = 1 NTRK2 G639L, n = 1 NTRK3 G623E) followed by the gatekeeper region (13%, n = 2/15: n = 1 NTRK1 F589L, n = 1 NTRK3 F617I). Two patients developed off-target alterations. One acquired BRAF V600E mutation and the other MET amplification. Interestingly, solvent front mutation loss was observed in two patients who transitioned to and progressed on a second-generation TRK TKI. One patient with a baseline NTRK1 G595R mutation developed polyclonal resistance with acquisition of KRAS G12A and NTRK1 G667A alterations as well as NTRK1 G595R loss. The other patient with NTRK3 G623R developed an NTRK3 F617I gatekeeper mutation with NTRK3 G623R loss. Conclusions: In NTRK fusion-positive cancers, on-target resistance preferentially involving the solvent front is more frequent than off-target resistance to first-generation TKI therapy. Furthermore, the sequential use of second-generation therapy appears to alter the evolutionary kinetics of mutation retention and acquisition.

The development of APS03118, a potent next-generation RET inhibitor for treating RET-inhibitor-resistant patients

e15107

Background: Oncogenic RET is an actionable target across a variety of cancers. Selective RET inhibitors selpercatinib and pralsetinib were recently approved by the FDA and EMA for patients with RET-dependent NSCLC and thyroid cancers. The solvent front mutations (SFMs) RET G810C/S/R have been identified as mechanisms of acquired resistance to both drugs. APS03118 is a novel next-generation RET inhibitor which is potent against a range of RET fusions and mutations including both SFMs and gatekeeper mutations. Methods: The selectivity, anti-RET activity, and intracranial efficacy of APS03118 were confirmed in vitro and in vivo in a variety of RET-dependent tumor models. Results: APS03118 was highly selective against a panel of 468 kinases and demonstrated 130-fold selectivity over VEGFR-2. In enzymatic assays, APS03118 showed low nanomolar potency against wild type RET and 25 RET mutations/fusions, including the inhibition of RET G810R/C/S (IC50 0.04-5 nM) and RET V804M/L/E (IC50 0.04-1 nM). APS03118 inhibited RET phosphorylation (IC50 < 15 nM) in Ba/F3 engineered RET cells (WT, G810R, V804M, M918T). In cell proliferation assays, APS03118 potently inhibited the proliferation of KIF5B-RET Ba/F3 (WT, V804M, V804L, M918T), CCDC6-RET Ba/F3 (WT, V804M, S904F), LC2/ad (CCDC6-RET), TT (RET C634W) (IC50 < 10nM); Ba/F3 RET G810R and G810S IC50 (8-65 nM). APS03118 demonstrated marked anti-tumor efficacy in vivo in RET-driven cell-derived (Ba/F3 KIF5B-RET, V804M, TT (C634W)) and patient-derived (KIF5B-RET, CCDC6-RET, CCDC6-RET V804M) xenograft tumor models at 10 mg/kg (TGI 87-108%). Tumors completely subsided in CCDC6-RET orthotopic brain model with a 100% survival rate. In the Ba/F3 KIF5B-RET G810R xenograft model, APS03118 30 mg/kg showed 90% TGI and was well tolerated, and RET G810 mutations often drive clinical progression on current RET inhibitors. The pharmacokinetic/pharmacodynamic relationship of APS03118 in Ba/F3 KIF5B-RET G810R and WT xenograft tumor model was investigated, and the sustained decrease of the phosphorylated RET were observed at 30 mg/kg with the plasma exposure exceed cell IC90. Conclusions: APS03118 is a novel highly selective next-generation RET inhibitor that possesses potent in vitro and in vivo activity against a diverse range of RET alterations, including SFMs-mediated resistance. APS03118 has received IND approval and Fast Track Designation from FDA, and a first-in-human phase 1 trial for patients with RET-driven solid tumors with activating RET alterations is planned for 2022.

Updated health-related quality of life of patients with TRK-fusion cancer treated with larotrectinib in clinical trials

6563

Background: NTRK gene fusions have been identified as oncogenic drivers in patients (pts) with TRK fusion cancer across multiple solid tumors. Larotrectinib, a highly selective, CNS-active TRK inhibitor has shown high response rates, durable disease control, and a favorable safety profile in pts with TRK fusion cancer and is approved in over 40 countries. Larotrectinib has demonstrated rapid health-related quality of life (HRQOL) improvement in a group of 57 adult and pediatric pts (Kummar et al, Curr Prob Canc 2021). Here, we report updated HRQOL results for larger group of pts treated with larotrectinib. Methods: HRQOL data were collected in two ongoing trials (NCT02576431, NCT02637687) of larotrectinib in pts with TRK-fusion cancer using the EORTC QLQ-C30, EQ-5D-5L questionnaires and were analyzed descriptively and longitudinally. Scores from the EORTC QLQ-C30 Global Health Status (GHS), EQ-5D-5L VAS range from 0 to 100, with higher scores indicating better QOL. We also calculated the proportion of pts with either below normal or normal and above normal HRQOL scores against values in the literature for the US general population. Results: By July 2021, 113 adults with TRK-fusion cancer had received larotrectinib and completed the baseline (BL) and ≥ 1 post-BL questionnaire. The majority of pts had clinically meaningful HRQOL improvements during treatment (Table). For EORTC QLQ-C30 GHS, most adults maintained or improved scores from BL at or above the normal population level category. HRQOL improvements (change from BL > 0) occurred after ̃2 months of treatment in 75% of adults. Median duration of pts with sustained improvement in EORTC QLQ-C30 GHS, and EQ-5D-5L VASs was 12.5 months (range, 1.8-34.1), and 12.9 months (range, 1.8-34.0), respectively. HRQOL results were consistent across multiple data cuts. Conclusions: Patients with TRK-fusion cancer treated with larotrectinib continued to have rapid, clinically meaningful, and sustained improvements in HRQOL. Clinical trial information: NCT02576431, NCT02122913, NCT02637687.

Clinical outcomes of immune checkpoint inhibitors in HER2-amplified non-small cell lung cancers

e21098

Background: HER2 (ERBB2) amplification is a distinct actionable oncogenic driver in 2-3% of non-small cell lung cancer (NSCLC). While HER2-targeted agents are now in development for lung cancers harboring HER2 mutations, the therapeutic landscape for patients with HER2 amplification is not well elucidated. Although immune checkpoint inhibitors (ICIs) alone or in combination with chemotherapy are widely used as treatment for NSCLC, little is known about the impact of ICIs in patients with HER2-amplified NSCLC. This study aimed to assess the efficacy of ICIs in this patient population. Methods: Patients with HER2-amplified NSCLC were identified from January 2014 to October 2021. HER2 amplification was detected by next generation sequencing (NGS) on the MSK-IMPACT platform. Clinicopathologic and molecular features, as well as response to therapy with ICIs were assessed. Patients were excluded if they harbored concurrent HER2 mutations, had localized disease, or received concurrent chemotherapy. Patient records were reviewed to evaluate overall survival (OS), progression free survival (PFS) and overall response rate (ORR). Results: Eighteen patients with metastatic HER2-amplified NSCLC who received ICI alone as first line treatment or subsequent therapy after progression met inclusion criteria. Histologic subtypes included adenocarcinoma (78%) and squamous cell carcinoma (22%). PD-L1 expression was available for 16 patients, with 69% having no expression of PD-L1. The median tumor mutation burden (TMB) was 9.2 mutations/Mb (range 3.0-35.4). The median OS was 11 months (95% CI: 4 to 37), with 6-month and 12-month survival being 67% (95% CI: 40% to 83%) and 49% (95% CI: 25% to 70%), respectively. Median PFS was 2 months (95% CI: 1 to 7). In the 15 patients that were assessed for response, the ORR was 0% (95% CI 0% to 19%), including 3 cases with PD-L1 expression of ≥ 50% and 9 cases with TMB ≥ 10 mutation/Mb. Conclusions: Patients with HER2-amplified NSCLC showed minimal response to immunotherapy, regardless of PD-L1 status and TMB. These findings underscore the importance of developing novel HER2-targeted agents for these patients with unmet medical need.

Updated efficacy and safety of larotrectinib in patients with tropomyosin receptor kinase (TRK) fusion lung cancer

9024

Background: Neurotrophic tyrosine receptor kinase ( NTRK) gene fusions have been identified as oncogenic drivers in a variety of tumor types, including lung cancer. Larotrectinib is a highly selective, central nervous system (CNS)-active TRK inhibitor that demonstrated an objective response rate (ORR) of 73% across 15 investigator-assessed patients (pts) with lung cancer (Drilon et al, JCO Precis Oncol 2022). We report data on an expanded cohort of pts with TRK fusion lung cancer treated with larotrectinib. Methods: Pts with TRK fusion lung cancer enrolled in two larotrectinib clinical trials (NCT02576431 and NCT02122913) were included for this analysis. Larotrectinib was administered at 100 mg twice daily. Response was assessed by independent review committee (IRC) per RECIST v1.1. Results: As of July 20, 2021, a total of 26 pts with TRK fusion lung cancer (24 non-small cell lung cancer, 1 atypical carcinoid, 1 neuroendocrine) were enrolled, including 10 pts with CNS metastases at baseline. Median age was 51.5 years (range 25.0–76.0). The gene fusions involved NTRK1 (n =21; 81%) or NTRK3 (n =5; 19%). Pts received a median of 2 prior lines of systemic therapies with 19 (73%) receiving ≥2. Among 23 pts evaluable per IRC, the ORR was 83% (95% confidence interval [CI] 61–95): two complete responses, 17 partial responses (PR), and four stable disease (SD). The median time to response was 1.8 months. Among 10 evaluable pts with baseline CNS metastases, the ORR was 80% (95% CI 44–97): eight PR and two SD. Median duration of response (DoR) and progression-free survival (PFS) were not reached; median follow-up was 12.9 and 14.6 months, respectively. The 24-month rates for DoR and PFS were 72% and 67%, respectively. Median follow-up for overall survival (OS) was 12.9 months. The 24-month and 36-month rates for OS were both 72%. For the 10 evaluable pts with CNS metastases, the 12-month DoR, PFS, and OS rates were 26%, 22%, and 78%, respectively. Duration of treatment for all pts evaluable per IRC ranged from 2.1 to 52.7+ months. At data cut-off, six pts had progressed, with all six continuing treatment post-progression for ≥4 weeks. Treatment-related adverse events (TRAEs) were predominantly Grade 1–2. Grade 3–4 TRAEs were reported in five pts (increased alanine aminotransferase, increased aspartate aminotransferase, hypersensitivity, myalgia, and increased weight). There were no treatment discontinuations due to TRAEs. Conclusions: In this larger dataset, larotrectinib demonstrated rapid and durable responses, extended survival, and a favorable long-term safety profile in pts with advanced lung cancer harboring NTRK gene fusions, including in pts with CNS metastases. These results support testing for NTRK gene fusions in pts with lung cancer. Clinical trial information: NCT02576431, NCT02122913.

Clinical characteristics and outcome of a large cohort of patients with primary central nervous system (CNS) tumors and tropomyosin receptor kinase (TRK) fusion

2052

Background: TRK fusions are detected in less than 3% of central nervous system (CNS) tumors. Given their rarity, there are limited data on the clinical course of affected patients. Methods: We contacted 166 oncology centers worldwide to retrieve data on patients with TRK fusion-driven CNS tumors. Data extracted included demographics, histopathology, TRK gene fusion, treatment modalities and outcomes. Results: Ninety-two patients with TRK fusion-driven primary CNS tumors were identified including 76 pediatric patients (82.6%), 15 adults (16.3%) and 1 not specified (1.1%). Median age at diagnosis was 4.4 years (range 0.0–78.3) and 58.7 % were male. NTRK2 gene fusions were found in 45 patients (48.9%), NTRK1 and NTRK3 aberrations were detected in 27 (29.3%) and 20 (21.7%), respectively. Tumor types included 56 high-grade gliomas (HGG; 60.9%), 20 low-grade gliomas (LGG; 21.7%), 4 embryonal tumors (4.3%) and 12 others (13.0%). Median follow-up was 40.5 months (range 3–226). During the course of their disease, 75 (81.5%) patients underwent surgery with a treatment intent, 67 (72.8%) patients received chemotherapy, 50 (54.3%) patients received radiation therapy, while 47 (51.1%) patients received NTRK inhibitors (6 as first line treatment). There were significant differences in the median progression-free (PFS) and overall survival (OS) between pediatric patients compared to adults. The pediatric median PFS was 32 months (95% CI: 15.5–48.5) compared to 8 months for the adult (95% CI: 4.5–11.5, p = 0.015). The pediatric median OS was 182 months (95% CI: 25.1–338.9) compared to 24 months (95% CI: 18.3–29.7 p < 0.001) for adult patients. There was no difference in the PFS of LGG compared to HGG. However, the OS was significantly worse for the HGG when compared to LGG (p = 0.039). The median OS for LGG was not reached and the median OS for HGG was 70 months (95% CI 7.5–132.5). Nineteen patients with HGG (38.0 % 19/50 evaluable patients) died compared to only one patient with LGG (5.6% 1/18 evaluable patients, p = 0.014). Conclusions: We report the largest cohort of patients with TRK fusion-driven primary CNS tumors. These results will help us to better understand clinical evolution and compare outcomes with ongoing clinical trials.

Suboptimal clinician awareness of appropriate NTRK fusion testing and TRK inhibitor use in solid tumors

229

Background: Since late 2018, 2 TRK inhibitors—larotrectinib and entrectinib—have been approved by the EMA and FDA for treating patients with advanced solid tumors harboring an NTRK fusion and progressive disease or no therapeutic alternatives. It is recommended that testing for NTRK fusions occur as early as possible after a diagnosis of advanced disease in patients with solid tumors to inform potential use of TRK inhibitors. Methods: Between April 2018 and April 2021, we conducted multiple live and online educational activities for oncology healthcare professionals (HCPs) on NTRK fusion testing and/or TRK inhibitor treatment for varied solid tumors. Each activity included polling questions designed to assess HCP knowledge and practice patterns. In this analysis, we assessed HCP responses to these questions to evaluate awareness of expert recommendations on NTRK fusion testing and the selection of TRK inhibitor therapy for appropriate patients. Results: In 6 live and online activities with data from April 2018 to April 2021, 29% of HCPs (n = 844) indicated that they ordered molecular profiling to test for NTRK fusions in all solid tumors in their current practice. Of note, low rates of testing were reported in TRK inhibitor/ NTRK testing-focused activities throughout this time period, with no significant increase over time. In assessing different patient cases across 8 activities where experts recommended TRK inhibitor therapy as optimal, many HCPs did not select a TRK inhibitor, with considerable variance by tumor type (Table). *For all cases, experts selected larotrectinib and/or entrectinib as optimal treatment. †HCP respondents. GBM, glioblastoma; GI, gastrointestinal; MSI-H, microsatellite instability-high; PD, progressive disease; PTC, papillary thyroid cancer.Conclusions: The rate of broad testing for NTRK fusions across patients with solid tumors remains low, and many HCPs lack awareness of when to consider a TRK inhibitor. Educational activities designed to address these deficiencies would be of clear benefit to HCPs treating patients with advanced solid tumors. A detailed analysis of HCP trends will be presented.[Table: see text]

Spectrum of BRAF Mutations and Gene Rearrangements in Ovarian Serous Carcinoma

Low-grade serous carcinoma (LGSC) is a rare type of ovarian cancer, which commonly arises from serous borderline tumor (SBT) and is characterized by frequent activating mutations in the mitogen-activated protein kinase pathway, including BRAF. The BRAF ^V600E mutation is associated with improved prognosis in SBT and LGSC, and responses to BRAF inhibitor therapy have been reported. We sought to characterize the clinicopathologic and molecular features of BRAF-driven tubo-ovarian and primary peritoneal serous tumors.

METHODS

Retrospective analysis of our institutional cohort of SBTs (n = 22), LGSCs (n = 119) and high-grade serous carcinomas (HGSCs, n = 1,290) subjected to targeted massively parallel sequencing was performed to identify cases with BRAF genetic alterations. Putative BRAF rearrangements were confirmed using targeted RNA sequencing and/or fluorescence in situ hybridization (FISH). BRAF^V600E oncoprotein expression was assessed by immunohistochemistry on selected cases.

RESULTS

BRAF somatic genetic alterations were identified in 29 of 1,431 (2%) serous tumors and included mutations (n = 24), gene rearrangements (n = 3), and amplification (n = 2). BRAF mutations were more frequent in SBTs (7 of 22; 32%) compared with LGSCs (11 of 119; 9%, P = .009) and HGSCs (6 of 1,290; 0.5%; P < .0001, SBT/LGSC v HGSC). The BRAF ^V600E hotspot mutation was most common (n = 16); however, other BRAF driver mutations were also detected (n = 8). BRAF mutations were often clonal or truncal in SBTs and LGSCs, but subclonal in most HGSCs. Pathogenic BRAF gene fusions were identified in LGSCs (n = 2) and HGSC (n = 1) and involved distinct fusion partners (AGK, MKRN1, and AGAP3). Three patients with BRAF-mutant LGSC were treated with targeted mitogen-activated protein kinase inhibitors, one of whom was maintained on therapy for over 3 years with clinical benefit.

CONCLUSION

Recognition of BRAF alterations beyond V600E mutation in LGSC may have clinical implications for appropriate targeted therapy selection.

Efficacy and safety of larotrectinib in adult and pediatric patients with tropomyosin receptor kinase (TRK) fusion-positive primary central nervous system tumors

2002

Background: Neurotrophic tyrosine receptor kinase ( NTRK) gene fusions are oncogenic drivers in various tumor types, including central nervous system (CNS) tumors. Larotrectinib is a first-in-class, highly selective TRK inhibitor approved for the treatment of adult and pediatric patients with TRK fusion cancer, with an objective response rate (ORR) of 78% across 175 adult and pediatric patients with various non-CNS cancers (McDermott et al, ESMO 2020). We report data on patients with TRK fusion-positive primary CNS tumors. Methods: Patients with primary CNS tumors harboring an NTRK gene fusion enrolled in two clinical trials (NCT02637687, NCT02576431) were identified. Larotrectinib was administered until disease progression, withdrawal, or unacceptable toxicity. Response was investigator assessed. Results: As of July 2020, 33 patients with TRK fusion-positive CNS tumors were identified: 19 high-grade gliomas (HGG), 8 low-grade gliomas (LGG), 2 glioneuronal tumors, 2 neuroepithelial tumors, 1 CNS neuroblastoma, and 1 small round blue cell tumor. The patients had gene fusions involving NTRK2 (n = 24; 73%), NTRK1 (n = 5; 15%), and NTRK3 (n = 4; 12%). Median age was 8.9 years (range 1.3–79.0); 26 patients were pediatric ( < 18 years). Patients were heavily pre-treated with 45% having 2 or more prior lines of systemic therapy. The ORR in all patients was 30% (95% CI 16–49): 3 complete responses (all in pediatric patients), 7 partial responses (2 pending confirmation), 20 stable disease (including 15 pts > 6 months), and 3 progressive disease. The ORR in patients with HGG and LGG were 26% (95% CI 9–51) and 38% (95% CI 9–76), respectively. In all patients, the 24-week disease control rate was 73% (95% CI 54–87). Twenty-three of 28 patients (82%) with measurable disease had tumor shrinkage. The median time to response was 1.9 months. Median duration of response (DoR) was not reached (95% CI 3.8–not estimable [NE]) at a median follow-up of 12.0 months. The 12-month DoR rate was 75% (95% CI 45–100). Median PFS was 18.3 months (95% CI 6.7–NE) at a median follow-up of 16.5 months. Median overall survival (OS) was not reached (95% CI 16.9–NE) at a median follow-up of 16.5 months, with a 12-month OS rate of 85% (95% CI 71–99). Duration of treatment ranged from 1.2 to 31.3+ months. Treatment-related adverse events (TRAE) were reported by 20 patients and were Grade 3–4 in 3 patients (9%). There were no treatment discontinuations due to TRAEs. Conclusions: In patients with TRK fusion-positive CNS tumors, larotrectinib demonstrated rapid and durable responses, high disease control rate, and a favorable safety profile. These results support testing for NTRK gene fusions in patients of all ages with CNS tumors. Clinical trial information: NCT02637687, NCT02576431.

BRCA reversion mutations in a pan-cancer cohort to reveal BRCA-dependence in select noncanonical BRCA-mutant histologies

3012

Background: Loss of BRCA1/2 function leads to homologous recombination deficiency (HRD) and can enhance platinum and PARP inhibitor sensitivity in breast, pancreas, prostate, and ovarian cancers. In BRCA-associated cancers, resistance can result from the development of BRCA1/2 reversion mutations, which restore BRCA1/2 function. By contrast, a BRCA mutation may be an incidental finding in other tumor histologies. Methods: To determine the distribution of reversion mutations in a pan-cancer cohort, the MSK-IMPACT clinical sequencing cohort was mined to identify patients who had both a germline BRCA1/2 mutation and a frameshift somatic reversion mutation that restored BRCA1/2 function. Whole exome resequencing was used to detect HRD signatures. Chart review enabled collection of data on treatment history in patients consented to germline testing. Results: Of the 33,277 patients with matched tumor and normal sequencing profiled in this study, 861 patients were found to have germline pathogenic BRCA1/2 alterations, including 347 (40%) in BRCA1 and 514 (60%) in BRCA2. Somatic BRCA1/2 driver alterations were also found in tumor tissue from an additional 447 patients, with 156 (35%) having BRCA1 mutations, and the remainder having alterations in BRCA2 (65%) . Among the 1,308 germline or somatic BRCA1/2 mutant tumors, we identified reversion mutations in 12 patients, all of whom were germline carriers of BRCA1/2, comprising 3 BRCA1 and 9 BRCA2 tumors. 7 patients consented to germline testing enabling review of clinical characteristics and treatment history, 5 of whom received PARP inhibitor or platinum-therapy prior to reversion detection. Ten of 12 tumors with reversion mutations were in canonical BRCA-associated cancers. Interestingly, reversion mutations were also found in patients with lung adenocarcinoma (n=1) and gastroesophageal junction adenocarcinoma (n=1). In both these non-canonical histologies, the reversion was detected following progression on platinum-based therapy. Whole exome resequencing of the lung tumor revealed the classic somatic molecular phenotypes of HRD that are characteristic of BRCA-dependent tumors, including in terms of large-scale transitions, HRD-loss of heterozygosity, signature 3, and the number of telomeric allelic imbalance score. Conclusions: Matched tumor and normal sequencing from a large cohort of patients with diverse cancer histologies reveals that reversion mutations are found across BRCA-associated cancer types. In rare cases, reversion mutations in BRCA1/2 following platinum-based therapy may be indicative of prior BRCA-dependence in select non-canonical tumor histologies.

Selpercatinib efficacy and safety in patients with RET-altered thyroid cancer: A clinical trial update

6073

Background: Selpercatinib, is a first-in-class, highly selective, CNS active and potent RET inhibitor approved in multiple countries for treatment of RET-fusion positive lung or thyroid cancers. Reported is an update of efficacy and safety results in RET-altered thyroid cancer, with a longer follow up (30 Mar 2020 data cutoff vs 16 Dec 2019) and additional enrolment. Methods: Patients (pts) with RET-mutant medullary thyroid cancer (MTC) and RET-fusion positive thyroid cancer (TC) were enrolled in the global (16 countries, 89 sites) Phase 1/2 LIBRETTO-001 trial (NCT03157128). The primary endpoint was objective response rate (ORR) per RECIST 1.1 by independent review committee (IRC). Secondary endpoints included duration of response (DoR), progression-free survival (PFS), clinical benefit rate (CBR; CR+PR+SD ≥16 weeks), and safety. The integrated analysis set (IAS, n = 143) includes efficacy evaluable MTC pts previously treated with cabozantinib and/or vandetanib (cabo/vande). The primary analysis set (PAS), a subset of IAS, is the first 55 enrolled pts. Cabo/vande naïve MTC pts (N = 112) and TC pts with prior systemic treatment (N = 22) were also analyzed. Safety population includes all pts who received ≥1 dose of selpercatinib (MTC N = 315; TC N = 42) by data cutoff. Results: For MTC patients, the ORR for IAS was 69.2%, in the PAS it was 69.1%, and 71.4% for cabo/vande naïve MTC pts. The ORR for TC pts (n = 22) was 77.3% (see table). Most treatment-emergent adverse events (TEAEs) were low grade; the most common (≥25% of MTC and/or TC pts treated with selpercatinib) were dry mouth, diarrhea, hypertension, fatigue and constipation for both MTC and TC pts, increased ALT/AST, peripheral edema and headache in MTC pts and nausea in TC pts. 4.8% of MTC and TC pts discontinued selpercatinib due to TEAEs but only 1.9% with MTC and none with TC discontinued due to treatment-related adverse events. Conclusions: In this updated analysis, selpercatinib continued to show marked and durable antitumor activity in pts with RET-altered thyroid cancers. Selpercatinib was well tolerated and no new safety concerns were identified. A global, randomized, phase 3 trial (LIBRETTO-531) evaluating selpercatinib compared to cabo/vande in kinase inhibitor naïve MTC pts is ongoing. Clinical trial information: NCT03157128. [Table: see text]

Efficacy and safety of zenocutuzumab in advanced pancreas cancer and other solid tumors harboring NRG1 fusions

3003

Background: NRG1 fusion proteins are oncogenic drivers in pancreas cancer and other solid tumors. They bind HER3, leading to HER2/HER3 heterodimerization and oncogenic transformation. The activity of zenocutuzumab (MCLA-128; zeno), a bispecific antibody targeting NRG1 fusion signaling in NRG1 fusion positive ( NRG1+) cancers, is being evaluated in the ongoing global multicenter phase 2 part of the eNRGy study and a global early access program (EAP). Methods: Enrolled patients (pts) have advanced NRG1+ pancreas cancer, non-small cell lung cancer (NSCLC), and other solid tumors previously treated with standard therapy, are ≥ 18 years-old, have ECOG ≤1, adequate organ function, and measurable disease (RECIST v1.1). Zeno dosing: 750 mg IV every 2 weeks until progression or unacceptable toxicity. Primary endpoint: investigator (INV)-assessed objective response rate (ORR). Secondary endpoints: ORR per central independent radiologist review, duration of response (DOR), and safety. Tumor imaging is conducted every 8 weeks. Results: 51 pts with NRG1+ cancer have received zeno, 37 in the eNRGy study and 14 pts in the EAP. As of 12 Jan 2021, treatment is ongoing in 27/51 pts (8/13 pancreas, 10/25 NSCLC, 9/13 other solid tumors). Among the 51 pts, 10 pts with pancreas cancer, 18 pts with NSCLC, and 5 pts with other solid tumors had measurable disease and had the opportunity for ≥1 tumor assessment (TA) and are included in this analysis. Among the 10 pts with pancreas cancer, median age was 49 y (range 34-72), 50% were male, 6/4 pts had ECOG 0/1, and all had metastatic disease and were KRAS wild-type. The median number of prior therapies was 3 (range 1-6). The INV-assessed confirmed ORR was 40% (4/10; 90% CI, 15;70), and for this cohort of pts, responses occurred at the first TA. Tumor regression was seen in 7/10 pts, and the disease control rate was 90% (90% CI, 61-100). A CA 19-9 decline of ≥ 50% was observed in 9/9 (100%) pts. DOR is pending. In the overall NRG1+ population, tumor regression was observed in 25 of 33 pts and confirmed INV-assessed responses were seen in 9 of 33 pts (ORR 27%; 90% CI, 15;43), including in pts who previously received afatinib. Zeno was well tolerated with no pts requiring dose reduction for toxicity. Across all cohorts, for individual AEs, grade 3 events were reported in ≤5% of pts, and there was a notable lack of cardiotoxicity and severe gastrointestinal or skin toxicity. Updated data from all cohorts (pancreas, NSCLC, other solid tumors) will be presented. Conclusions: Zeno induces rapid and major radiologic tumor regression and biomarker responses in heavily-pretreated metastatic KRAS wild-type NRG1+ pancreas cancer, with minimal toxicity. Zeno is a promising novel targeted therapeutic option for pts with NRG1+ cancers. Clinical trial information: NCT02912949.

Efficacy of selpercatinib after prior systemic therapy in patients with RET mutant medullary thyroid cancer

6074

Background: Selpercatinib is a first-in-class, CNS active, highly selective, and potent RET kinase inhibitor which has demonstrated durable antitumor activity in patients (pts) with RET altered thyroid cancer and is approved in multiple countries for the treatment of RET fusion+ lung or thyroid cancers. As response rates to cancer therapy usually decline on subsequent lines of therapy, the efficacy of selpercatinib was examined in the context of the last prior therapy received before trial enrollment. Methods: Pts with RET mutant medullary thyroid cancer (MTC) previously treated with multikinase inhibitors (cabozantinib and/or vandetanib) were enrolled in the global LIBRETTO-001 trial (NCT03157128). This post-hoc exploratory intrapatient analysis, based on March 30, 2020 data cutoff date, was performed to compare the retrospective physician-reported objective response rate (ORR) from the last systemic therapy prior to enrollment, as reported in pts case reports, to ORR by independent review committee per RECIST 1.1 with selpercatinib treatment, with each patient serving as his/her own control. Results: Efficacy-evaluable pts, 64% male, 90% white with a median age of 58 years, received prior therapy for MTC (n = 143). Pts had a median of 2 (range 1-8) prior systemic regimens. The ORR on selpercatinib (69%) was markedly higher than for the last prior therapy (10%) received before enrollment. ORR improvements with selpercatinib were observed regardless of prior therapy: cabozantinib (66% vs 14%) or vandetanib (71% vs 12%). Fewer pts had progressive disease as their best overall response with selpercatinib (2/143; 1.4%) compared to last prior therapy (33/143; 23.1%). Notably selpercatinib achieved 62% ORR in pts that did not respond to their previous line of therapy prior to enrolment. This shift from non-responder to responder on selpercatinib therapy was consistent regardless of prior cabozantinib or vandetanib treatment, where pts achieved 57% and 61% ORR respectively when subsequently treated with selpercatinib. In contrast, only 3% of patients did not respond to selpercatinib after a previous response to the immediate prior therapy. Similarly, 5% and 2% of patients were non-responders on selpercatinib after a prior response with cabozantinib and vandetanib therapy respectively. Conclusions: Prior to selpercatinib, response with previous multikinase therapy was rare. By contrast, selpercatinib demonstrated robust efficacy regardless of response to or specific prior therapy in pts with RET mutant MTC. Clinical trial information: NCT03157128.

Response to selpercatinib versus prior systemic therapy in patients (pts) with RET fusion+ non-small-cell lung cancer (NSCLC)

9032

Background: Selpercatinib, a first-in-class highly selective, potent, CNS-active RET kinase inhibitor, is approved in multiple countries for treatment of RET fusion+ lung or thyroid cancers. Selpercatinib demonstrated durable antitumor activity in previously treated pts with RET fusion+ NSCLC in an ongoing Phase 1/2 trial, LIBRETTO-001 (Besse et al., ASCO 2021). Methods: Pts with RET fusion+ NSCLC enrolled in the global, multicenter, LIBRETTO-001 trial (NCT03157128; 16 countries, 89 sites). Primary endpoint was objective response rate (ORR). Secondary endpoints included progression-free survival, duration of response, and safety. This post-hoc intrapatient analysis was based on a 30 March 2020 data cutoff date. Historical physician-reported best overall response (BOR) from last systemic therapy received prior to enrollment was compared with selpercatinib BOR by independent review committee per RECIST v1.1, with each patient serving as his/her own control. Results: In efficacy-evaluable pts (N = 218) who previously received platinum-based chemotherapy (chemo), median pt age was 61 years, the majority with ECOG of 0/1 (37%/61%), with a median of 2 (range: 1-15) prior systemic therapies. Overall, 57% of patients responded to selpercatinib while 16% responded to the immediate prior therapy. ORR improvements with selpercatinib were observed regardless of prior therapy: chemotherapy + immune checkpoint inhibitor (ICI) (57% vs 14%), single-agent ICI (48% vs 3%), or chemotherapy (58% vs 15%). A total of 108 patients (49%) did not respond to immediate prior therapy but responded to selpercatinib. Fewer patients had progressive disease as their BOR with selpercatinib (2%) compared to the immediate prior therapy (28%). The median duration of therapy for selpercatinib was notably extended compared with that of the immediate prior therapy (11.8 vs. 3.4 months, respectively). Conclusions: In pts with RET fusion+ NSCLC treated on LIBRETTO-001, systemic therapies administered prior to enrollment achieved less meaningful clinical benefit than selpercatinib. Selpercatinib demonstrated consistent efficacy regardless of the type of prior therapy. Clinical trial information: NCT03157128.

Long-term efficacy and safety of larotrectinib in patients with TRK fusion-positive lung cancer

9109

Background: Neurotrophic tyrosine receptor kinase ( NTRK) gene fusions have been identified as oncogenic drivers in a diverse array of tumor types including lung cancer. Larotrectinib is a first-in-class, highly selective, central nervous system (CNS)-active tropomyosin receptor kinase (TRK) inhibitor approved for the treatment of adult and pediatric patients (pts) with TRK fusion cancer, with an objective response rate (ORR) of 78% across multiple non-CNS cancers (McDermott et al, ESMO 2020). Here, we report the updated data on pts with lung cancer treated with larotrectinib. Methods: Pts with lung cancer harboring a NTRK gene fusion enrolled in two clinical trials (NCT02576431 and NCT02122913) were identified for this analysis. Larotrectinib 100 mg PO BID was administered on a continuous 28-day schedule until disease progression, withdrawal, or unacceptable toxicity. Response was assessed by the investigator per RECIST v1.1. Results: As of July 20, 2020, a total of 20 pts with TRK fusion-positive lung cancer (19 with non-small cell lung cancer and 1 with small cell lung cancer) were enrolled. Median age was 48.5 years (range 25.0–76.0). The gene fusions involved NTRK1 (n = 16; 80%) or NTRK3 (n = 4; 20%). Pts were heavily pre-treated with a median of 3 systemic therapies (range 0–6). Among 15 evaluable pts, the confirmed ORR was 73% (95% CI 45–92): 1 complete response, 10 partial responses (PR), 3 stable disease (SD) and 1 progressive disease (PD). The median time to response was 1.8 months. Among 8 evaluable pts with baseline measurable and non-measurable CNS metastases, the ORR was 63% (95% CI 25–91): 5 PR, 2 SD, and 1 PD. In all evaluable pts, the 12-month rates for duration of response and progression-free survival were 81% and 65%, respectively. Median overall survival was 40.7 months (95% CI 17.2 to not estimable) at a median follow-up of 16.2 months. Duration of treatment ranged from 0.03+ to 51.55+ months. Adverse events (AEs) were predominantly Grade 1–2. Treatment-related AEs were reported in 16 pts, of which 2 experienced Grade 3 events (myalgia, hypersensitivity, weight increase). There were no treatment discontinuations due to AEs. Conclusions: These data confirm that larotrectinib is highly active with rapid and durable responses, extended survival benefit, and a favorable long-term safety profile in pts with advanced lung cancer harboring NTRK gene fusions, including in pts with CNS metastases. These results underscore the importance of screening for NTRK gene fusions in pts with lung cancer. Clinical trial information: NCT02576431 and NCT02122913.

Tumor-agnostic precision immuno-oncology and somatic targeting rationale for you (TAPISTRY): A novel platform umbrella trial

TPS3154

Background: Actionable genomic alterations are found in many solid tumors in pediatric and adult populations. Identifying such alterations can match patients (pts) to genome-driven therapies. Although TRK and immune checkpoint inhibitor therapies have tumor-agnostic approval for NTRK-rearranged and tumor mutational burden (TMB)-high cancers, respectively, similar approvals remain an unmet need for other genome-driven cancers, limiting pt access to potentially active therapies. Platform master protocol studies leveraging comprehensive next-generation sequencing (NGS) are a pragmatic means of evaluating multiple genome-driven therapies in rare biomarker-selected populations. Contemporary study designs include adult and pediatric pts to expand care across age groups. Methods: TAPISTRY (NCT04589845) is a phase 2, global, open-label, multi-cohort study evaluating the efficacy and safety of targeted therapy or immunotherapy, as single agents or in combination, in pts with unresectable, locally advanced/metastatic solid tumors. Eligible pts have tumors that harbor genomic alterations or are TMB-high by NGS (Foundation Medicine or CLIA/equivalent-certified laboratory). General inclusion criteria: PD on prior treatment/no available acceptable treatment; measurable disease (by RECIST v1.1, RANO, INRC), adequate ECOG/equivalent PS and end organ function. Pts will be assigned to treatment according to eligibility criteria for biomarker-defined cohorts (Table). Pediatric pts may be enrolled if age-appropriate formulations/dosages are established. Samples will be taken for central NGS biomarker testing at baseline (tissue/blood), tumor assessments (blood) and at response/PD (optional tissue/blood). Tumor assessments (CT, MRI, PET) will be completed at baseline then every 6–8 weeks, depending on cohort. Primary endpoint: confirmed ORR by independent review committee (IRC; RECIST v1.1). Key secondary endpoints: ORR (by investigator [INV], per RECIST/INRC); DoR, CBR, PFS, time to CNS PD (by IRC and INV, per RECIST/INRC); intracranial efficacy (Cohorts A–D; per RANO [primary brain tumors]/RECIST [baseline CNS mets]); OS; patient-reported outcomes; safety; pharmacokinetics and immunogenicity (Cohorts D and F). Treatment will continue until PD, loss of clinical benefit, unacceptable toxicity, discontinuation or death. Target enrollment is 650 pts at 100+ sites based on screening 40,000+ pts; 3 pts enrolled as of 9 Feb 2021. Clinical trial information: NCT04589845. [Table: see text]

Overall survival with circulating tumor DNA-guided therapy in advanced non-small cell lung cancer

9009

Background: The effectiveness of circulating tumor DNA (ctDNA) at matching patients to life prolonging therapy has been studied mostly in small cohorts with limited follow up. The prognostic value of ctDNA alterations, particularly those absent on tissue, is also unclear. To address these questions, we studied survival outcomes in a prospective cohort of patients (N = 1002) with non-small cell lung cancer (NSCLC). Methods: Adults with metastatic or recurrent NSCLC were eligible if they had no known driver mutation or a known driver with progression following targeted therapy. Patients were enrolled at Memorial Sloan Kettering Cancer Center (New York, NY) starting October 21, 2016; analysis here is from a snapshot November 1, 2020. All patients had ctDNA sequenced via the Resolution ctDx Lung platform. To reduce inclusion of incidental germline mutations, we excluded non-functionally significant mutations with an allele frequency 35-65% that were present in gnomAD. Patients could also receive, at their provider’s discretion, tissue sequencing with MSK-IMPACT, which filters germline and clonal hematopoietic (CH) mutations with matched white blood cell sequencing. We performed survival analyses using Cox proportional hazards models from time of diagnosis of advanced disease to death, left truncating at time of study entry. Results: Of 1002 patients, 348 (35%) were treated with targeted therapy; in 181 of these (52%) the targetable alteration was detected in ctDNA. Patients treated with targeted therapy had prolonged survival whether matched by tissue-based methods (HR 0.39, 95%CI 0.30-0.51) or ctDNA (HR 0.47, 95%CI 0.37-0.61). These benefits persisted across multiple subgroups. ctDNA alterations themselves were associated with worse survival (HR 2.2, 95%CI 1.8-2.8), in a manner that scaled with allele fraction and burden. Of 401 patients with time-matched tissue sampling, 62 (15%) had ctDNA alterations that were absent on IMPACT (“unique” ctDNA alterations). Three such patients had unique ctDNA EGFR T790M mutations leading to changes in therapy. However, unique ctDNA alterations were generally associated with worse survival than no ctDNA alterations (HR 2.5, 95%CI 1.7-3.7) and even tissue-matched ctDNA alterations (HR 1.7, 95%CI 1.1-2.4). Of 98 unique ctDNA mutations, 48 (49%) were detectable in tissue at subthreshold levels, 12 (12%) were filtered by IMPACT as CH or germline, and 38 mutations (39%) were absent even at subthreshold levels. ctDNA alteration burden correlated with radiographic disease extent. In multivariate models with radiographic disease extent and other clinical variables, ctDNA alterations were the strongest independent predictor of worse survival. Conclusions: Our results show that ctDNA may match patients to life-prolonging targeted therapy and have prognostic importance. ctDNA may provide data about a patient’s cancer missed by spatially restricted tissue sequencing. Clinical trial information: NCT01775072.

Updated overall efficacy and safety of selpercatinib in patients (pts) with RET fusion+ non-small cell lung cancer (NSCLC)

9065

Background: Selpercatinib, a first-in-class highly selective and potent, CNS-active RET kinase inhibitor, is approved in multiple countries for treatment of RET fusion+ lung or thyroid cancers. Here we report an update of efficacy and safety results which provide a longer follow up and increased number of patients (safety population: N = 345 vs N = 329). Methods: Pts with RET fusion+ NSCLC enrolled in the global, multicenter, ongoing LIBRETTO-001 trial (NCT03157128; 16 countries, 89 sites) were included in this analysis. Pts with the opportunity to be followed ≥6 months from their first dose were included in the efficacy-evaluable population for these analyses. Integrated analysis set (IAS) included 218 NSCLC pts with prior platinum-chemotherapy. Primary analysis set (PAS) was a subset of the IAS and included the first 105 consecutively enrolled pts. The treatment-naïve population included 48 efficacy-evaluable pts. Primary endpoint was objective response rate (ORR, RECIST v1.1) by independent review committee (IRC). Secondary endpoints included ORR by investigator, duration of response (DoR), progression-free survival (PFS), clinical benefit rate (CBR; CR+PR+SD ≥16 weeks), and safety. Safety population (N = 345) included all pts with NSCLC who received ≥1 selpercatinib dose by data cutoff (30 Mar 2020). Results: In pts with prior treatment (N = 218) and treatment-naïve (N = 48) pts, 56% and 60% were female, with a median pt age of 61 and 64 years, respectively. The ORR with selpercatinib was 57% in the IAS, 64% in the PAS, and 85% in the treatment-naïve population (Table). In both the IAS and PAS, the median DoR was 17.5 months, median PFS was 19.3 months at median follow-up of 12.0 and 15.7 months, respectively (Table). The most common treatment-emergent adverse events (TEAEs) reported in ≥25% of pts were dry mouth, diarrhea, hypertension, increased ALT/AST, edema peripheral, and fatigue. Twenty-five pts (7%) permanently discontinued due to TEAEs, with 10 pts (3%) discontinuing selpercatinib due to treatment-related AEs as per investigator. Conclusions: In this updated data set, selpercatinib continued to demonstrate durable antitumor activity in pts with RET-fusion+ NSCLC. Selpercatinib was well-tolerated with a safety profile consistent with previous reports. A global, randomized, phase 3 trial (LIBRETTO-431) evaluating selpercatinib compared with standard frontline therapy is ongoing. Clinical trial information: NCT03157128. [Table: see text]

Response to immune checkpoint inhibition as monotherapy or in combination with chemotherapy in metastatic ROS1-rearranged lung cancers

9049

Background: ROS1 fusions are oncogenic drivers in various cancers types, including 1-3% of non-small cell lung cancers (NSCLCs). Immunotherapy approvals for NSCLC include ROS1-rearranged carcinomas, but the activity of immune checkpoint inhibition (ICI) as monotherapy or in combination with chemotherapy (chemo-ICI) therapy, as well as the immunophenotypic characteristics of these tumors, have not been described in a large data set. Methods: In this multi-institutional study, patients with ROS1-rearranged NSCLC were identified retrospectively. Tumor PD-L1 expression and tumor mutational burden (TMB) were assessed as part of routine clinical care. In patients who received ICI monotherapy or chemo-ICI in the metastatic setting, time to treatment discontinuation (TTD) and objective response rate (ORR; RECIST v. 1.1) were calculated. TTD was assessed with Kaplan-Meier methods; patients remaining on treatment were censored at last follow up. Results: 184 patients with ROS1-rearranged NSCLC were identified. Among 146 PD-L1 evaluable cases, PD-L1 expression was < 1% in 60 (41%), 1-49% in 35 (24%) and ≥50% in 51 (35%) tumors. Ninety-two of 100 (92%) TMB-evaluable tumors had < 10 mutations/megabase (mut/Mb). TMB was significantly lower for ROS1-rearranged NSCLCs (n = 97) vs. ROS1-wild type tumors (n = 5,380) evaluated with next-generation sequencing using MSK-IMPACT (median 2.6 vs. 5.9 mut/Mb, p < 0.001). Twenty-eight patients received ICI monotherapy and 11 patients received chemo-ICI. The median TTD was 2.1 months (95% CI: 1.0-4.2; n = 28) for single-agent ICI therapy and 10 months (95% CI: 4.7-14.1; n = 11) for chemo-ICI therapy. The ORR was 13% (2/16 RECIST-evaluable; 95% CI: 2-38%) for ICI monotherapy and 83% (5/6 RECIST-evaluable; 95% CI: 36-100%) for chemo-ICI therapy. There was no difference in PD-L1 tumor expression (p = 0.9) or TMB (p = 0.8) between responders and non-responders and no correlation between PD-L1 tumor expression (rho = 0.16, p = 0.6) or TMB (rho = 0.03, p = 0.9) and maximum change in sum of target lesions. Conclusions: Most ROS1-rearranged NSCLCs have low or no PD-L1 expression and low TMB. The activity of checkpoint inhibitor monotherapy is disappointing in ROS1-driven NSCLC. In contrast, combination chemoimmunotherapy can achieve clinically meaningful activity.

Intra-patient comparison from larotrectinib clinical trials in TRK fusion cancer: An expanded dataset

3114

Background: Larotrectinib is a highly selective, CNS-active tropomyosin receptor kinase (TRK) inhibitor that demonstrated rapid and durable responses in three phase I/II single-arm studies of patients (pts) with TRK fusion cancer. In single-arm studies the growth modulation index (GMI) can be used to provide a comparative analysis. GMI is an intra-patient comparison that uses pts as their own control by comparing progression-free survival (PFS) on current therapy to time to progression or treatment failure (TTP) on the most recent prior therapy; namely the ratio of PFS/TTP (EMA Guidelines. Guideline on the Evaluation of Anticancer Medicinal Products in Man, EMA/CHMP/205/95 Rev.5). A GMI ratio ≥1.33 has been used as a threshold of meaningful clinical activity. In a previous analysis of 122 pts with TRK fusion cancer treated with larotrectinib, 84 pts (69%) had a GMI ≥1.33. Conversely, 38 pts (31%) had a GMI < 1.33, but of these, 9 pts were ongoing treatment and censored for PFS as of July 2019 (Italiano et al, ESMO 2020). Here, we report the GMI of this initial group with a longer follow-up as well as an expanded dataset to more accurately assess the treatment effect of larotrectinib in pts with TRK fusion cancer previously treated with ≥1 line of therapy. Methods: Pts with TRK fusion cancer from three clinical trials on larotrectinib treatment with ≥1 prior line of systemic therapy were eligible for retrospective GMI analysis. TTP on the prior line of therapy was investigator-assessed. PFS on larotrectinib was determined by independent review committee per RECIST v1.1. Pts who had not progressed were censored as of date of last visit. Kaplan–Meier (KM) analyses were used to estimate median GMI, in addition to median PFS and TTP. The data cut-off was July 2020. Results: With an extended follow up of the original 122 pts, 90 (74%) pts had a GMI ≥1.33, including 6 of the 9 pts who were previously censored with a GMI < 1.33 and ongoing treatment; 6 pts (5%) had a GMI ≥1 to < 1.33 and 26 (21%) had a GMI < 1. The KM estimated median GMI increased from 7.6 (95% CI 5.7–88.0) to 9.5 (95% CI 5.7–17.4). In the expanded dataset of 140 pts, 103 pts (74%) had GMI ≥1.33, 7 (5%) had a GMI ≥1 to < 1.33 and 30 (21%) had a GMI < 1. Six of the 37 pts with a GMI < 1.33 were censored and still ongoing treatment. The KM estimated median GMI was 8.9 (95% CI 6.2–17.4). Among pts who had received 1, 2, or ≥3 prior lines of therapy, 74%, 65%, and 80%, respectively, had GMI of ≥1.33. Median TTP on the prior therapy was 3.0 months (95% CI 2.1–3.5) and median PFS on larotrectinib was 33.0 months (95% CI 16.6–34.9). Conclusions: With a longer follow-up, nearly three-quarters of pts with TRK fusion cancer treated with larotrectinib had a prolonged PFS compared to their most recent prior therapy. These results further validate the use of larotrectinib in treating patients with TRK fusion cancer. Clinical trial information: NCT02576431, NCT02122913, NCT02637687.

Oncologist management of NTRK fusion-positive NSCLC improves after virtual patient simulation participation

e23008

Background: Although relatively rare, neurotrophic receptor tyrosine kinase (NTRK) fusions, represent a clinically relevant subgroup of NSCLC that can derive benefit from targeted therapies. Relatively quick and durable responses have been achieved with these targeted therapies in advanced NSCLC and intracranial activity has also been observed. The objective of this study was to determine if an online, virtual patient simulation (VPS)-based continuing medical education (CME) intervention improved performance of oncologists in using appropriate strategies to diagnose and manage patients with NTRK fusion-positive advanced NSCLC. Methods: The CME intervention consisted of two patient cases presented in a VPS platform that allowed learners to order lab tests, diagnoses and treatments in a manner matching the scope and depth of actual practice. Clinical decisions made by the learners using open field entries within an EHR interface were analyzed and, after each decision, tailored clinical guidance (CG) was provided based on current evidence and expert recommendation. Learner decisions were collected post-CG and compared with each user’s baseline (pre-CG) data using a McNemar’s test to determine P values. Results were then aggregated for the two cases based on clinical decisions and stratified by practice setting. The activity posted July 31, 2020; data were collected through December 1, 2020. Results: Overall significant improvements were seen after CG in clinical decisions made by oncologists in both the community and academic settings [reported as % absolute improvement (% correct pre-CG vs % correct post-CG); P value]. Conclusions: This analysis demonstrated that VPS that immerses and engages oncologists in an authentic and practical learning experience can significantly improve evidence-based clinical decisions related to the diagnosis and management of patients with NTRK fusion-positive advanced NSCLC. Despite the improvements, additional educational activities are needed to address any residual gaps and further increase oncologists’ ability in this clinical setting.[Table: see text]

Long-term efficacy and safety of larotrectinib in an integrated dataset of patients with TRK fusion cancer

3108

Background: Neurotrophic tyrosine receptor kinase ( NTRK) gene fusions encode tropomyosin receptor kinase (TRK) fusion proteins, which are oncogenic drivers in various tumor types. Larotrectinib is a first-in-class, highly selective, CNS-active TRK inhibitor approved to treat adult and pediatric patients with TRK fusion cancer. Larotrectinib demonstrated an objective response rate (ORR) of 78% and a median progression-free survival (PFS) of 36.8 months in an integrated analysis of 175 patients with non-primary CNS TRK fusion cancer (McDermott et al, ESMO 2020). We report updated efficacy and safety data with longer follow-up in an expanded dataset. Methods: Data were pooled from three clinical trials of patients with non-primary CNS TRK fusion cancer treated with larotrectinib. Larotrectinib was administered until disease progression, withdrawal, or unacceptable toxicity. Response was assessed by investigators using RECIST v1.1. Data cutoff: July 20, 2020. Results: As of data cutoff, 218 patients were treated with larotrectinib, of which 206 were evaluable for efficacy. There were 21 different tumor types, the most common being soft tissue sarcoma (STS [46%], including infantile fibrosarcoma [20%] and other STS [26%]), thyroid (13%), salivary gland (11%), lung (9%), and colorectal (5%). The median age was 38.0 years (range 0.1–84.0). Patients were heavily pretreated with 45% having received 2 or more prior lines of systemic therapy; 27% had 0 prior lines of systemic therapy. The ORR was 75% (95% CI 68–81): 45 (22%) complete response, 109 (53%) partial response (PR), 33 (16%) stable disease (SD), and 13 (6%) progressive disease (PD). Nineteen patients had brain metastases at baseline, with 15 evaluable for efficacy. The ORR for patients with brain metastases was 73% (95% CI 45–92): 11 PR, 2 SD, and 2 PD. Among all evaluable patients, the median time to response was 1.8 months (range 0.9–9.1). With a median follow up of 22.3 months, the median duration of response was 49.3 months (95% CI 27.3–not estimable). Treatment duration ranged from 0.03+ to 60.4+ months. Median PFS was 35.4 months (95% CI 23.4–55.7) with a median follow up of 20.3 months. At a median follow-up of 22.3 months, median overall survival (OS) was not reached and 36-month OS was 77% (95% CI 69–84). Treatment-related adverse events (TRAEs) were mainly Grade 1–2, with 18% having Grade 3–4 TRAEs. Only 2% of patients discontinued due to TRAEs. Conclusions: These results highlight the importance of testing for NTRK gene fusions in patients with cancer because the majority of patients with TRK fusion cancer treated with larotrectinib had long-term clinical benefit. The safety profile continued to be favorable and no new safety signals were identified. Clinical trial information: NCT02576431, NCT02122913, NCT02637687.

Clinical implications of drug-induced liver injury in early-phase oncology clinical trials

BACKGROUND

Data on drug-induced liver injury (DILI) and acute liver failure (ALF) in modern phase 1 oncology trials are limited, specifically with respect to the incidence and resolution of DILI and the safety of drug rechallenge.

METHODS

This study reviewed all patients who were recruited to phase 1 oncology trials between 2013 and 2017 at Memorial Sloan Kettering Cancer Center. Clinicopathologic data were extracted to characterize DILI, and attribution was assessed on the basis of data prospectively generated during the studies. Logistic regression models were used to explore factors related to DILI and DILI recurrence after drug rechallenge.

RESULTS

Among 1670 cases recruited to 85 phase 1 trials, 81 (4.9%) developed DILI. The rate of DILI occurrence was similar for patients in immune-based trials and patients in targeted therapy trials (5.0% vs 4.9%), as was the median time to DILI (5.5 vs 6.5 weeks; P = .48). Two patients (0.12%) met the criteria of Hy's law, although none developed ALF. The DILI resolved in 96% of the patients. Pretreatment factors were not predictive for DILI development. Thirty-six of the 81 patients underwent a drug rechallenge, and 28% of these patients developed DILI recurrence. Peak alanine aminotransferase during the initial DILI was associated with DILI recurrence (odds ratio, 1.04; 95% confidence interval, 1.0-1.09; P = .035).

CONCLUSIONS

In modern phase 1 oncology trials, DILI is uncommon, may occur at any time, and often resolves with supportive measures. Rechallenging after DILI is feasible; however, the high rate of DILI recurrence suggests that clinicians should consider the severity of the DILI episode and treatment alternatives.

Correlation between overall response rate and progression-free survival/overall survival in comparative trials involving targeted therapies in molecularly enriched populations

3588

Background: Randomized trials involving agents targeting oncogene addicted tumors have greatly increased over the past decade. Whether clinical response rates can predict or correlate with efficacy measures such as progression-free survival (PFS) or overall survival (OS) has not been established in molecularly enriched patient populations. In this meta-analysis, we investigated whether improvements in objective response rate (ORR) in comparative trials using targeted agents could serve as a potential surrogate endpoint for improvements in PFS or OS in populations with oncogene addicted cancer. Methods: CT.gov and MEDLINE databases were queried (using commercial text mining software I2E) for randomized, phase 3 clinical trials based on the following prospectively defined criteria: (1) use of agents targeting EGFR activating mutations (erlotinib, gefitinib, afatinib, dacomitinib, osimertinib), ALK and ROS1 rearrangements (crizotinib, ceritinib, alectinib), BRAF V600E or V600K mutations (dabrafenib), and BCR-ABL fusion protein (imatinib, dasatinib, nilotinib, ponatinib); (2) must include molecularly enriched trial populations (biomarker subgroup data included if available); (3) control arms should not include targeted agents directed towards those molecularly enriched populations. ORR, OS, and PFS data were manually extracted from the relevant studies and correlative analyses (weighted Pearson correlation) were performed. Results: 61 trials were identified with 15 ultimately meeting the prespecified criteria. ORR effect size (both the ORR difference and log odds ratio) and the log PFS hazard ratio were strongly correlated (-0.78, p-value = 0.0007). No significant correlation was found between ORR and OS. Conclusions: In our analyses, a strong correlation between ORR and PFS was found in randomized clinical trials investigating agents targeting oncogene-driven cancers. Establishing a correlation between ORR and OS was limited, most probably due to confounding factors such as treatment cross-over following progression, number of subsequent therapies and long post-progression survival in this setting. These findings further warrant the use of ORR as a surrogate for PFS in biomarker-driven studies.

The next-generation RET inhibitor TPX-0046 is active in drug-resistant and naïve RET-driven cancer models

3616

Background: RET fusions/mutations drive oncogenesis in lung and thyroid cancers, and several other malignancies. Selective RET inhibitors (selpercatinib/pralsetinib) are active in patients with these cancers; unfortunately, resistance often occurs. On-target resistance includes the acquisition of solvent front mutations (SFMs i.e. RET G810 substitutions). TPX-0046 is a structurally differentiated RET inhibitor that is potent against a range of RET fusions and mutations including SFMs. Methods: The rationally-designed, compact, macrocyclic RET/SRC inhibitor TPX-0046 was characterized in RET-driven in vitro and in vivo tumor models. Results: In enzymatic assays, TPX-0046 showed low nanomolar potency against wild-type RET and 18 RET mutations/fusions. It was potent against SRC and spared VEGFR2/KDR. TPX-0046 inhibited RET phosphorylation (IC50 < 10 nM) in tumor cell lines (LC2/ad, CCDC6-RET; TT, RET C634W) and Ba/F3 engineered RET models (WT, G810R). In cell proliferation assays, TPX-0046 inhibited KIF5B-RET Ba/F3, LC2/ad, and TT cells with IC50 values ~1 nM. Ba/F3 RET engineered cells with SFMs (e.g. G810C/R/S) were potently inhibited by TPX-0046 (mean proliferation IC50 1–17 nM). TPX-0046 demonstrated marked in vivo anti-tumor efficacy in RET-driven cell-derived and patient-derived xenograft tumor models. In a Ba/F3 KIF5B-RET xenograft model, a single dose of 5 mg/kg TPX-0046 inhibited > 80% of RET phosphorylation (corresponding mean free plasma concentration: 51 nM). At 5 mg/kg BID, tumor regression was observed in RET-dependent xenograft models, including those that harbor RET SFMs: TT, CTG-0838 PDX (NSCLC, KIF5B-RET), CR1520 PDX (CRC, NCOA4-RET), Ba/F3 KIF5B-RET, and Ba/F3 KIF5B-RET G810R. Conclusions: TPX-0046 is a unique next-generation RET inhibitor that possesses potent in vitro and in vivo activity against a diverse range of RET alterations, including SFM-mediated resistance. A phase 1/2 trial for RET inhibitor-resistant and naïve RET-driven cancers is on-going (NCT04161391).

Targeted therapy based on germline analysis of tumor-normal sequencing (MSK-IMPACT) in a pan-cancer population

1500

Background: Tumor mutational profiling for identification of somatic alterations for targeted treatment is increasingly being performed in advanced cancer patients (pts). We sought to assess the clinical utility of germline mutation profiling for targeted therapeutic interventions in a pan-cancer patient population. Methods: All pts who had germline genetic testing through a prospective protocol via a next-generation sequencing panel (MSK-IMPACT) were identified (N=11,975) from 2015-5/2019. The medical record of pts with likely pathogenic/pathogenic germline (LP/P) alterations in genes with known therapeutic targets were reviewed to identify germline-targeted treatment either in a clinical or research setting. Results: We identified 2,043 (17.1%) pts who harbored LP/P variants in a cancer predisposition genes including 777 (6.5%) in genes with potentially targetable therapeutic implications: 416 BRCA1/2, 149 DNA mismatch repair genes (Lynch syndrome, LS), 122 ATM, 45 PALB2, 26 RAD51C/D, 7 RET, 4 TSC, 3 PTCH1, 2 ALK, 1 EGFR, 1 MET and 1 KIT. Of those with advanced disease (n=554), 45.3% received targeted therapeutic treatment (Table) including 50.9% BRCA1/2, 58.3% LS (67.4% of microsatellite-high LS cases), 41.7% PALB2, 36.8% RAD51C/D and 19.3% ATM carriers. Of patients receiving a poly (ADP-ribose) polymerase inhibitor (PARP-I) in the setting of a BRCA1/2 mutation, 55.1% had breast or ovarian cancer; however, 44.8% had other tumors, including pancreas, prostate, bile duct, gastric, wherein the drug was given in a research setting. Among PALB2 pts receiving PARP-Is, 53.3% (8/15) had breast or pancreas cancer; 46.7% had cancer of the prostate, ovary or unknown primary. Conclusions: In our pan-cancer analysis, 6.5% of pts harbored a targetable germline variant highlighting the importance of germline analysis in advanced cancer pts for selection of both FDA-approved treatments and clinical trial participation with germline-targeted therapeutics. [Table: see text]

Early ctDNA response assessment for prediction of platinum sensitivity in small cell lung cancer

9067

Background: Small cell lung cancer (SCLC) is an aggressive disease, characterized by inevitable chemotherapy resistance and rapid progression. We hypothesized that circulating tumor DNA (ctDNA) analysis can rapidly identify sensitivity to platinum-based therapy. Methods: Patients with SCLC at Memorial Sloan Kettering Cancer Center underwent serial plasma collections, including prior to the start of treatment and prior to Cycle 2 Day 1 of therapy (C2D1). Tumor mutations were identified from pre-treatment biopsies by MSK-IMPACT and/or pre-treatment plasma by CAncer Personalized Profiling by deep Sequencing (CAPP-Seq). Median variant allele fraction (VAF) of all mutations was monitored on subsequent blood draws using CAPP-Seq. Progression free survival (PFS) was measured from the time of first pre-treatment blood draw. Results: Plasma was collected from 19 patients treated with carboplatin and etoposide, including three who received concurrent atezolizumab. Seven were female, and mean age was 64.5 years. ctDNA was detected in 17 patients (89%), including in the two patients in our series with limited stage disease. The most common mutations were in TP53 and RB1 in 14 and 6 patients, respectively. Fourteen patients had available plasma at C2D1. At baseline prior to treatment, median VAF did not differ significantly between radiologic responders and non-responders (9.4% versus 30.3%, p = 0.35). After one cycle of chemotherapy, the VAF percent decrease was significantly more in responders versus non-responders (-96.9% versus -10.3%, p < 0.001). Median VAF was therefore significantly lower by C2D1 in patients who responded compared to non-responders (0.51% versus 27.2%, p = 0.02). Those who ultimately responded to therapy all had a > 2 fold decrease in VAF by C2D1. With a median follow-up of 180 days, PFS was significantly longer in patients with > 2 fold decrease in VAF by C2D1 (6.4 versus 1.9 months, log rank p < 0.001). Conclusions: A 2-fold decrease in plasma VAF by C2D1 predicted platinum-sensitivity in SCLC and was associated with longer PFS. ctDNA may permit early assessment of benefit and expedite alternative treatment options for those without significant decrease in median VAF after one cycle of therapy.

TRIDENT-1: A global, multicenter, open-label Phase II study investigating the activity of repotrectinib in advanced solid tumors harboring ROS1 or NTRK1-3 rearrangements

TPS9637

Background: Repotrectinib is a next-generation ROS1/TRK inhibitor with > 90-fold greater potency than crizotinib against ROS1 and > 100-fold greater potency than larotrectinib against TRK. Preclinical studies demonstrated inhibitory activity of repotrectinib against ROS1 resistance mutations, including the solvent-front mutation (SFM) G2032R. In the phase 1 portion of the study, repotrectinib was found to be well tolerated with encouraging antitumor activity including a 91% confirmed overall response (cORR) in TKI-naïve ROS1+ NSCLC pts. In ROS1+ NSCLC pts who received 1 prior chemo and 1 prior TKI, the cORR was 57% at the clinical dose of 160 mg QD or above. Intra-cranial (IC) activity was observed in ROS1+ NSCLC pts with measurable CNS disease (100% IC-ORR in TKI-naïve and 75% IC-ORR in patients with 1 prior TKI). Encouraging antitumor activity was observed in pts with NTRK+ solid tumors. Methods: A global phase 2 study was initiated and is actively enrolling. The primary endpoint for the Phase 2 study is cORR assessed by BICR (Blinded Independent Central Review) using RECIST v1.1, in each expansion cohort in pts with advanced solid tumors that harbor a ROS1 or NTRK1/2/3 gene fusion. Secondary endpoints include duration of response (DOR), progression-free survival (PFS), overall survival (OS), IC-ORR, IC-PFS, and quality of life assessments. All pts need to have RECIST 1.1 measurable disease confirmed by BICR and ECOG performance score ≤1. Repotrectinib is administered at 160 mg QD for 14 days and, if tolerated, the dose can be increased to 160 mg BID. Approximately 320 pts (≥12 years old) will be enrolled into 6 defined expansion cohorts, depending on the status of previous treatment with TKIs and cancer types (see table below). Clinical trial information: NCT03093116 . [Table: see text]

Efficacy and safety of entrectinib in patients (pts) with NTRK-fusion positive (NTRK-fp) solid tumors: An updated integrated analysis

3605

Background: NTRK gene fusions lead to transcription of chimeric TRK proteins with overexpressed kinase function. Entrectinib is a potent inhibitor of TRKA/B/C. In phase 1/2 studies (ALKA, STARTRK-1, STARTRK-2; EudraCT 2012-000148-88; NCT02097810; NCT02568267), entrectinib was effective in pts with NTRK-fp solid tumors. We present updated data in a larger population with longer follow-up. Methods: In this integrated analysis of adult pts from 3 phase 1/2 trials (data cut-off 31 Oct 2018), tumors were assessed by blinded independent central review (BICR) with RECIST v1.1 (end of cycle 1; then every 8 wks). Primary endpoints were overall response rate (ORR) and duration of response (DOR). Secondary endpoints were progression-free survival (PFS), overall survival (OS), efficacy in pts with/without baseline CNS disease, and safety. Results: There were 74 evaluable pts with advanced/metastatic NTRK-fp solid tumors (Table). Median duration of survival follow-up in all pts was 14.2 mo (range 0.1–29.7). BICR ORR was 63.5% (95% CI 51.5–74.4), with 5 complete responses (6.8%). Median BICR DOR was 12.9 mo (95% CI 9.3–NE); median BICR PFS was 11.2 mo (95% CI 8.0–15.7); median OS was 23.9 mo (16.0–NE). In pts with no baseline CNS disease (investigator-assessed; n=55), BICR ORR was 65.5% (95% CI 51.4–77.8) and median BICR DOR in responders was 12.9 mo (95% CI 9.3–NE). In pts with baseline CNS disease (investigator-assessed; n=19), BICR ORR was 57.9% (95% CI 33.5–79.8) and median BICR DOR in responders was 6.0 mo (95% CI 4.2–NE). Safety was in line with that previously reported; the most common ≥grade 3 treatment-related AEs were weight gain (8, 7.1%), anemia (8, 7.1%), and fatigue (7, 6.2%). Conclusions: In this updated analysis, including more pts and longer follow-up, entrectinib continued to demonstrate clinically meaningful responses in pts with NTRK-fp solid tumors, with and without baseline CNS disease. Clinical trial information: NCT02097810, NCT02568267 . [Table: see text]

Clinical characteristics, genomic features, and recurrence risk of early-stage MET exon 14 mutant non-small cell lung cancer (NSCLC)

9042

Background: MET exon 14 alterations occur in ~3% of patients (pts) with NSCLC. Although clinical and genomic features of MET exon 14 mutant (mut) NSCLC are better characterized in the metastatic setting, less is known about early-stage disease for this molecular subtype. Methods: Clinicopathologic and genomic data were collected from patients (pts) with resected stage I-III MET exon 14 mutant NSCLC at the Dana-Farber Cancer Institute (DFCI) and the Memorial Sloan Kettering Cancer Center (MSKCC). We estimated the disease-free survival (DFS) and overall survival (OS) of patients from the date of surgical resection. The prevalence of MET exon 14 mutations in stage I-III NSCLC was assessed using OncoPanel NGS v3.0 at DFCI. Results: The prevalence of MET exon 14 alterations in resected tumors of pts with stage I-III NSCLC at DFCI using Oncopanel v3 was 2.8% (17/613) overall: 2.9% (16/542) in non-squamous and 1.4% (1/71) in squamous histology. We identified 131 pts with resected stage I-III (I = 73, II = 28, III = 30) MET exon 14 mut NSCLC at DFCI (Oncopanel v1-v3) and MSKCC (MSK-IMPACT), with a median age of 71 years (yrs) (range: 43-88). There were no significant differences in sex, smoking status, or type of MET alteration across stages. In stage I resected tumors there was a higher proportion of adenocarcinoma histology compared to stages II and III (p = 0.009). The median harmonized TMB (mTMB) was similar across stages (p = 0.43). Common genomic co-alterations included MET amplification (amp) (5.3%), CDK4/ 6 amp (19.1%), MDM2 amp (35.1%), TP53 mut (17.6%) and CDKN2A/ B loss (9.2%). The median DFS in stage I, II, and III NSCLC was 8.3 yrs (95% CI: 3.1-8.3), 2.6 yrs (95% CI: 1.0-2.6), and 2.1 yrs (95% CI: 0.7-2.7), respectively (p = 0.017). The median OS in stage I, II, and III NSCLC was 9.2 yrs (95% CI: 8.5 -10.5), not reached (NR) (95% CI: NR-NR), and 4.1 yrs (95% CI: 3.6-4.1), respectively (p = 0.052). Concurrent MET amp was independently associated with worse DFS (HR: 4.9, 95% CI: 1.8-13.1; p = 0.002) in multivariate analysis. Conclusions: MET exon 14 mutations are present in 2.8% of resected stage I-III NSCLCs. Given the prevalence of this molecular alteration in early-stage NSCLC, clinical trials exploring the role of adjuvant and neoadjuvant MET targeted therapies in this population may be warranted.

Intracranial activity of selpercatinib (LOXO-292) in RET fusion-positive non-small cell lung cancer (NSCLC) patients on the LIBRETTO-001 trial

9516

Background: Patients with RET fusion-positive NSCLC have an ~50% lifetime prevalence of developing central nervous system (CNS) metastases. Selpercatinib is a highly selective oral RET inhibitor with CNS penetration. Its intracranial antitumor activity was previously demonstrated in an orthotopic RET fusion-positive preclinical model. The activity of selpercatinib in RET fusion-positive NSCLC patients with CNS metastases was evaluated as a prespecified subgroup analysis in LIBRETTO-001, a registrational phase 1/2 trial (NCT03157128). Methods: This global (89 sites, 16 countries) trial enrolled patients with advanced RET-altered solid tumors, including patients with RET fusion-positive advanced NSCLC with baseline CNS metastases. The selpercatinib recommended phase 2 dose was 160 mg twice daily, dosed orally in 28-day cycles. CNS metastases were assessed by MRI/CT scan at baseline, then every 8 weeks for 1 year, and every 12 weeks thereafter. The primary endpoint for this analysis was intracranial objective response rate (ORR, confirmed; RECIST v1.1) as assessed by independent review committee (IRC). Secondary endpoints included intracranial duration of response (DoR) by IRC. To be included in the efficacy analysis, patients were required to have adequate follow-up time (opportunity for ≥6 months follow-up from the first dose). Analyses were based on 17Jun2019 data cutoff date. Results: 79 patients with RET fusion-positive NSCLC and baseline CNS metastases were enrolled. Per IRC, 22 of 79 patients had measurable (≥10 mm) CNS disease; 14 of the 22 patients had adequate follow-up time for analysis. This efficacy-evaluable population had a median age of 64 yrs (range 43-80), ECOG PS 0/1 = 21% / 79%, and all had prior systemic therapy. 5 of the 14 patients received prior intracranial radiotherapy; all radiotherapy was completed > 2 months prior to selpercatinib. The intracranial ORR in the 14 patients was 93% (n = 13; 95% CI = 66.1 – 99.8), including 2 complete responses (14%) and 11 partial responses (79%). The median intracranial DoR was 10.1 months (95% CI = 6.7 – NE), with CNS progression events (n = 5) or death (n = 1) reported in 6 of 13 responders. The remaining responders (n = 7) were ongoing and censored. Presentation will include updated IRC data as of 16Dec2019. Conclusions: Selpercatinib had marked intracranial anti-tumor activity in RET fusion-positive NSCLC patients with CNS metastases. Tumor responses were durable, independently-confirmed, and observed in patients with prior systemic chemotherapy. Clinical trial information: NCT03157128 .

Quality of life of adults and children with TRK fusion cancer treated with larotrectinib compared to the general population

3614

Background: NTRK gene fusions occur in diverse tumor types in adults and children. The selective TRK inhibitor, larotrectinib, has shown high response rates, durable disease control, and a favorable safety profile in patients (pts) with TRK fusion cancer. We report an expanded quality of life (QoL) analysis for pts treated with larotrectinib. Methods: QoL data were collected in two trials of larotrectinib in pts with TRK fusion cancer using EORTC QLQ-C30 (adults) and PedsQL (children) questionnaires, and were analyzed descriptively and longitudinally. EORTC QLQ-C30 global health scores (GHS) and PedsQL total scores range from 0 to 100, with higher scores indicating better QoL. We calculated the proportion of pts with normal/above and below normal QoL scores compared to values in the literature for the US general population. Results: By July 2019, 126 pts with TRK fusion cancer (74 adults, 24 children ≥2 yrs, and 28 infants <2 yrs) had received larotrectinib and completed baseline (BL) and ≥1 post-BL questionnaire. Most pts had clinically meaningful QoL improvements that reached or exceeded the minimally important difference (Table); a positive change from BL was also seen in infants: mean best change of 12.0 (SD 13.8). Of 52 adults with BL EORTC QLQ-C30 GHS at or above the population norm, 51 remained in this category on treatment and 1 moved into the below normal category. Of 22 adults with BL scores below the population norm, 20 moved into the normal/above normal category. All 9 children aged ≥2 yrs with BL PedsQL scores at or above the population norm remained in this category on treatment. Of 15 children with BL scores below the population norm, 10 moved into the normal/above normal category. Sustained QoL improvements (change from BL ≥0) occurred by 2 months of treatment in 69% of adults and 75% of children. Median duration of sustained improvement in EORTC QLQ-C30 GHS and PedsQL total score was 12.0 months (range 1.7–20.3) and not estimable (range 1.1–23.0), respectively. Conclusions: Adults and children with TRK fusion cancer treated with larotrectinib had rapid, clinically meaningful, and sustained improvements in QoL. Clinical trial information: NCT02576431, NCT02637687 . [Table: see text]

Selpercatinib (LOXO-292) in patients with RET-fusion+ non-small cell lung cancer

3584

Background: Selpercatinib (LOXO-292) is a highly selective and potent small molecule RET kinase inhibitor. Here we report an update on the efficacy and safety of selpercatinib in RET-fusion+ non-small-cell lung cancer (NSCLC). Methods: Patients with RET-fusion+ NSCLC were enrolled to the Phase 1/2 LIBRETTO-001 trial (NCT03157128), a global, multicenter trial (16 countries, 89 sites). Following the Phase 1 dose escalation portion of the trial, patients received the recommended dose of 160 mg orally twice daily. Each cycle was 28 days. The primary endpoint was objective response rate (ORR) per RECIST 1.1. Secondary endpoints included duration of response (DoR) and safety. Per health authority agreement, the primary analysis set was defined as the first 105 consecutively enrolled patients previously treated with platinum-based chemotherapy. Treatment-naïve patients were analyzed separately. All analyses were based on a 16-Dec-2019 data cutoff date. Results: In the primary analysis set of platinum-treated patients (median of 3 prior systemic regimens; range 1-15), the ORR by investigator assessment was 70% (95% CI 59.8–78.1, n = 73/105). Responses did not differ by fusion partner or number or type of prior therapies, including anti-PD-1/PD-L1 agents and off-label multikinase inhibitor use. The median DoR was 20.3 months (95% CI 15.6–24.0) with 45 of 73 (62%) responders censored at a median follow-up of 14.8 months. Among 39 treatment-naïve patients, the ORR by investigator assessment was 90% (95% CI 75.8–97.1, n = 35/39, including 2 responses pending confirmation). Median DoR was not reached with 27 of 33 (82%) confirmed responses ongoing at a median follow-up of 7.4 months. In the safety analysis set consisting of all selpercatinib dosed patients (N = 702), the most common treatment-related adverse events (TRAEs) that occurred in ≥15% of patients were dry mouth (33.3%), increased AST (24.5%), increased ALT (23.8%), hypertension (23.2%), diarrhea (19.7%), and fatigue (16.8%). Only 2% (14 of 702) of patients discontinued selpercatinib for TRAEs. Conclusions: Selpercatinib achieved marked and durable antitumor activity in patients with RET-fusion+ NSCLC. Selpercatinib was well tolerated. Efficacy data assessed by independent review committee based on the 16-Dec-2019 data cutoff date will be presented. Clinical trial information: NCT03157128 .

MSK-ACCESS for noninvasive somatic mutation profiling of lung cancers utilizing circulating tumor DNA

3529

Background: Circulating cell-free DNA (cfDNA) next-generation sequencing (NGS) is a promising strategy for non-invasive molecular profiling of cancers. MSK-ACCESS (Analysis of Circulating cfDNA to Evaluate Somatic Status) is a hybridization-capture targeted NGS assay that detects somatic variants in select exons of 129 genes with matched white blood cell sequencing. We present the initial clinical experience with MSK-ACCESS among patients with advanced non-small cell lung cancer (NSCLC). Methods: Patients with stage IV NSCLC underwent prospective MSK-ACCESS testing at initial diagnosis or progression of disease on targeted therapy between June 2019 and January 2020. A subset of patients had matched tissue-based NGS testing with the MSK-IMPACT 468 gene assay. We assessed oncogenic driver detection, turnaround time, plasma-tissue concordance, and matching to therapy. National Comprehensive-Cancer Network designated driver alterations were included in evaluation of tissue-plasma concordance (EGFR, ALK, KRAS, MET, RET, BRAF, HER2, ROS1, NTRK). Turnaround time was compared by a two-sided Wilcoxon signed-rank test. Results: A total of 201 patients with NSCLC had MSK-ACCESS testing at initial diagnosis (n = 79) or following progression of disease (n = 122). The median turn-around-time from plasma collection to MSK-ACCESS report was 16 days (range: 9 – 36 days) compared to 19 days from lab receipt of tissue to report (range: 12 – 57) for MSK-IMPACT (p < 0.001). Among patients with a driver detected on MSK-ACCESS, 100% (92/92) had an identical driver detected on MSK-IMPACT. Among patients with a driver detected on MSK-IMPACT, 75% (92/123) had an identical driver detected on MSK-ACCESS. This rate was similar among patients who were treatment-naive (74%; 64/86) and had disease progression (76%, 28/37) at the time of MSK-ACCESS. MSK-ACCESS identified driver alterations that directly guided first-line targeted therapy (n = 18) with response in all patients with available radiographic follow-up (n = 10), including a patient without confirmatory tissue testing. MSK-ACCESS identified resistance alterations among patients with disease progression including EGFR T790M, EGFR C797S, ROS1 G2032R, as well as a BRAF fusion. Conclusions: MSK-ACCESS successfully identified driver alterations with high concordance to tissue-based testing, directly guided patients to therapy with clinical responses, and detected known and novel resistance mechanisms. This assay warrants further clinical development to guide and facilitate precision oncology.