Abstract 918: Real-world clinical characteristics and treatment (tx) outcomes by co-mutation status in patients (pts) with KRAS G12C-mutated non-small cell lung cancer (NSCLC)

Background: KRAS mutations occur in ~30% of NSCLC and KRAS G12C is the most common subtype (~40%). Co-mutations can impact NSCLC prognosis and tx response.

Methods: This retrospective study used the nationwide (US-based) de-identified Flatiron Health-Foundation Medicine clinico-genomic database (FH-FMI CGDB; January 1, 2011 to March 31, 2022). De-identified data originated from ~280 US cancer clinics (~800 sites of care). This study is based on tissue-based assay (FoundationOne CDx). Pts were aged ≥18 years; had KRAS G12C-mutated, advanced/metastatic NSCLC, and had received ≥1 line of tx, with 1L tx initiated after October 1, 2016. Pts were categorized by presence (m) or absence (wt) of single co-mutations in STK11, KEAP1, or TP53; pts with EGFR, ALK, ROS1, BRAF, MET, or NTRK alterations were excluded. Key endpoints included overall survival (OS) and real-world progression-free survival (rwPFS). Statistical methods included a univariate Cox hazard model.

Results: Among 847 pts with KRAS G12C-mutated NSCLC, co-mutations of STK11 were seen in 24%, KEAP1 in 14%, and TP53 in 51%. Based on non-missing records (82%), low tumor mutational burden (<10 mut/Mb) was more frequent in the STK11m vs wt group (72% vs 55%; p<0.001), not significantly different in the KEAP1m vs wt group (53% vs 60%; p=0.145), and less frequent in pts with TP53m vs wt (50% vs 69%; p<0.001). Negative PD-L1 status (<1%) was more frequent in pts with STK11 (50% vs 18%; p<0.001) or KEAP1 (41% vs 23%; p<0.001) mutations, and less frequent in pts with TP53 mutations (15% vs 37%; p<0.001). STK11 or KEAP1 co-mutations were associated with shorter rwPFS and OS, particularly in pts treated with immunotherapy (IO)-based 1L tx (Table 1). TP53 status did not significantly impact pt outcomes in the 1L setting.

Conclusions: In this real-world analysis, STK11 or KEAP1 co-mutations were associated with PD-L1-negative tumors and poor outcomes with IO-based tx in KRAS G12C-mutated NSCLC.

Table 1. rwPFS and OS by co-mutation status, and OS by 1L treatment and co-mutation status rwPFS and OS by co-mutation status rwPFS All (N=846) STK11m (n=206) STK11wt (n=640) KEAP1m (n=121) KEAP1wt (n=725) TP53m (n=429) TP53wt (n=417) Median, months (95% CI) 5.0 (4.5-5.7) 4.0 (3.1-4.9) 5.6 (4.9-6.2) 3.8 (2.7-4.8) 5.6 (4.7-6.2) 5.3 (4.6-6.1) 4.7 (4.0-5.7) HR (95% CI); p value - 1.38 (1.16-1.64); <0.001 1.46 (1.18-1.80); <0.001 0.87 (0.75-1.01); 0.07 OS All (N=847) STK11m (n=206) STK11wt (n=641) KEAP1m (n=121) KEAP1wt (n=726) TP53m (n=429) TP53wt (n=418) Median, months (95% CI) 11.9 (10.2-14.3) 9.4 (7.2-13.8) 12.4 (10.8-15.0) 7.6 (5.4-9.4) 13.5 (11.0-15.1) 11.0 (9.2-14.4) 12.7 (10.4-15.3) HR (95% CI); p value - 1.40 (1.15-1.70); <0.001 1.59 (1.26-2.00); <0.001 0.98 (0.83-1.17); 0.85 OS by 1L treatment and co-mutation status IO + chemotherapy STK11m (n=106) STK11wt (n=228) KEAP1m (n=53) KEAP1wt (n=281) TP53m (n=162) TP53wt (n=172) Median, months (95% CI) 6.9 (4.5-9.4) 11.3 (9.0-14.8) 7.9 (4.5-10.3) 10.2 (7.7-12.9) 9.3 (6.6-11.9) 10.9 (7.2-14.0) HR (95% CI); p value 1.75 (1.33-2.31); <0.0001 1.60 (1.13-2.26); 0.01 1.04 (0.80-1.36); 0.75 IO monotherapy STK11m (n=33) STK11wt (n=181) KEAP1m (n=29) KEAP1wt (n=185) TP53m (n=111) TP53wt (n=103) Median, months (95% CI) 9.7 (2.8-16.9) 16.1 (10.7-23.3) 5.7 (3.9-14.3) 16.6 (10.8-23.0) 15.1 (9.1-22.4) 14.6 (8.9-23.0) HR (95% CI); p value 1.54 (0.97-2.46); 0.07 1.81 (1.12-2.90); 0.01 0.96 (0.68-1.37); 0.83 Chemotherapy only STK11m (n=56) STK11wt (n=188) KEAP1m (n=28) KEAP1wt (n=216) TP53m (n=130) TP53wt (n=114) Median, months (95% CI) 18.6 (10.2-22.8) 13.5 (9.5-15.3) 7.8 (5.0-17.4) 14.5 (11.1-16.3) 12.0 (8.9-16.0) 15.0 (11.1-19.5) HR (95% CI); p value 0.84 (0.57-1.25); 0.40 1.31 (0.82-2.10); 0.26 1.12 (0.81-1.54); 0.49 CI, confidence interval; HR, hazard ratio.

Citation Format: Marcelo V. Negrao, Wen-Hsing Wu, Colin R. Lindsay, Rafael Caparica, Vincent Prêtre, Yehrim Kang, Nydia Caro, Anna Farago, Fen Ye, Gilberto de Castro Jr. Real-world clinical characteristics and treatment (tx) outcomes by co-mutation status in patients (pts) with KRAS G12C-mutated non-small cell lung cancer (NSCLC) [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 918.

Abstract CT033: KontRASt-01: A phase Ib/II, dose-escalation study of JDQ443 in patients (pts) with advanced, KRAS G12C-mutated solid tumors

Background: KRAS G12C oncogenic mutations occur in ~13% of non-small cell lung cancers (NSCLCs) and up to 4% of other solid tumors. JDQ443 is a selective, covalent, orally bioavailable, investigational KRASG12C inhibitor that irreversibly traps KRASG12C in the inactive, GDP-bound state. JDQ443 is structurally unique and forms novel interactions with KRAS in the switch II pocket.

Methods: KontRASt-01 (NCT04699188) is a Phase Ib/II, open-label, multicenter, dose-escalation and dose-expansion trial of JDQ443 as monotherapy or in combination with TNO155 (SHP2 inhibitor) and/or tislelizumab (anti-PD-1 monoclonal antibody). Primary objectives of dose escalation are to assess safety and tolerability, and identify the maximum tolerated doses (MTDs) and/or recommended doses (RDs) and regimens for future studies. The primary objective of dose expansion is to assess efficacy. Key inclusion criteria: advanced, KRAS G12C-mutated solid tumors; previous standard-of-care treatment; age ≥18 yrs; ECOG PS 0-1. Key exclusion criteria for the JDQ443 monotherapy arm: active brain metastases, prior KRASG12C inhibitor treatment. Here, we present preliminary results for JDQ443 monotherapy dose escalation.

Results: As of Nov 3, 2021, 39 pts were treated with JDQ443 PO continuously across 4 dose levels: 200 mg once daily (QD) (n=10), 400 mg QD (n=11), 200 mg twice daily (BID) (n=11), and 300 mg BID (n=7). Median age was 60 yrs (range 26-76), median prior lines of therapy was 3 (range 1-7), and indications included NSCLC (n=20) and colorectal cancer (CRC) (n=16). Median duration of exposure was 9.1 wks (range 0.9-21), with ongoing treatment in most pts (61.5%) at the time of cut-off. Treatment-related adverse events (TRAEs) occurred in 25 (64.1%) pts. Most TRAEs were Grade (Gr) 1-2. Four Gr 3 TRAEs occurred in 4 (10.3%) separate pts; there were no Gr 4-5 TRAEs. The most common TRAEs (occurring in ≥10% of pts) were fatigue (25.6%), nausea (15.4%), edema (12.8%), pruritus (10.3%), and vomiting (10.3%). There was one DLT (Gr 3 fatigue) and one treatment-related serious AE (Gr 3 photosensitivity reaction), each in separate pts treated at 300 mg BID. TRAEs led to dose reduction in 1 pt and discontinuation in 1 pt. A MTD was not reached. The RD was declared as 200 mg BID. At the RD, PK and PD modeling for JDQ443 predicted average KRASG12C target occupancy of >90% in >82% of pts. Using an efficacy cut-off date of Dec 13, 2021, for the 20 pts with NSCLC among the same 39 pts, the ORR (confirmed complete response or partial response) by RECIST 1.1 was 30.0% (6/20) across dose levels and 43.0% (3/7) at the RD. Additional data will be available at the time of presentation.

Conclusions: JDQ443 demonstrates an acceptable safety and tolerability profile, with early signs of clinical activity in pts with NSCLC. Enrollment is ongoing to NSCLC and CRC dose-expansion groups for JDQ443 monotherapy at the RD, and to JDQ443 + TNO155 dose escalation.

Citation Format: Daniel S. Tan, Toshio Shimizu, Benjamin Solomon, Rebecca S. Heist, Martin Schuler, Maria J. De Miguel Luken, Anas Gazzah, Martin Wermke, Christophe Dooms, Herbert H. Loong, Neeltje Steeghs, Enriqueta Felip, Conor E. Steuer, Eric van Cutsem, Ross A. Soo, Ashley C. Jaeger, Jaeyeon Kim, Kun Xu, Xueying Chen, Xiaoming Cui, Heather Burks, Anna Farago, Philippe A. Cassier. KontRASt-01: A phase Ib/II, dose-escalation study of JDQ443 in patients (pts) with advanced, KRAS G12C-mutated solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT033.

Subtype heterogeneity and epigenetic convergence in neuroendocrine prostate cancer

Neuroendocrine carcinomas (NEC) are tumors expressing markers of neuronal differentiation that can arise at different anatomic sites but have strong histological and clinical similarities. Here we report the chromatin landscapes of a range of human NECs and show convergence to the activation of a common epigenetic program. With a particular focus on treatment emergent neuroendocrine prostate cancer (NEPC), we analyze cell lines, patient-derived xenograft (PDX) models and human clinical samples to show the existence of two distinct NEPC subtypes based on the expression of the neuronal transcription factors ASCL1 and NEUROD1. While in cell lines and PDX models these subtypes are mutually exclusive, single-cell analysis of human clinical samples exhibits a more complex tumor structure with subtypes coexisting as separate sub-populations within the same tumor. These tumor sub-populations differ genetically and epigenetically contributing to intra- and inter-tumoral heterogeneity in human metastases. Overall, our results provide a deeper understanding of the shared clinicopathological characteristics shown by NECs. Furthermore, the intratumoral heterogeneity of human NEPCs suggests the requirement of simultaneous targeting of coexisting tumor populations as a therapeutic strategy.

Neuroendocrine carcinomas (NECs) arise from different anatomic sites, but have similar histological and clinical features. Here, the authors show that the epigenetic landscape of a range of NECs converges towards a common epigenetic state, while distinct subtypes occur within neuroendocrine prostate cancer contributing to intratumor heterogeneity in clinical samples.

Coronavirus Disease 2019 Infection in a Patient Population with Lung Cancer: Incidence, Presentation, and Alternative Diagnostic Considerations

Introduction

Lung cancer is associated with severe coronavirus disease 2019 (COVID-19) infections. Symptom overlap between COVID-19 and lung cancer may complicate diagnostic evaluation. We aimed to investigate the incidence, symptoms, differential diagnosis, and outcomes of COVID-19 in patients with lung cancer.

Methods

To determine an at-risk population for COVID-19, we retrospectively identified patients with lung cancer receiving longitudinal care within a single institution in the 12 months (April 1, 2019 to March 31, 2020) immediately preceding the COVID-19 pandemic, including an “active therapy population” treated within the last 60 days of this period. Among patients subsequently referred for COVID-19 testing, we compared symptoms, laboratory values, radiographic findings, and outcomes of positive versus negative patients.

Results

Between April 1, 2019 and March 31, 2020, a total of 696 patients received longitudinal care, including 406 (58%) in the active therapy population. Among 55 patients referred for COVID-19 testing, 24 (44%) were positive for COVID-19, representing a cumulative incidence of 3.4% (longitudinal population) and 1.5% (active therapy population). Compared with patients who were COVID-19 negative, those who were COVID-19 positive were more likely to have a supplemental oxygen requirement (11% versus 54%, p = 0.005) and to have typical COVID-19 pneumonia imaging findings (5 versus 56%, p = 0.001). Otherwise, there were no marked differences in presenting symptoms. Among patients who were COVID-19 negative, alternative etiologies included treatment-related toxicity (26%), atypical pneumonia (22%), and disease progression (22%). A total of 16 patients positive for COVID-19 (67%) required hospitalization, and seven (29%) died from COVID-related complications.

Conclusions

COVID-19 was infrequent in this lung cancer population, but these patients experienced high rates of morbidity and mortality. Oncologists should maintain a low threshold for COVID-19 testing in patients with lung cancer presenting with acute symptoms.

Abstract CT127: Phase I and expanded access experience of LOXO-195 (BAY 2731954), a selective next-generation TRK inhibitor (TRKi)

Background: Larotrectinib, a selective TRKi, is now FDA approved for pediatric and adult TRK-fusion solid tumors, regardless of tumor origin. Emergent TRK kinase mutations are a common mechanism of resistance to TRKis. LOXO-195, a selective TRKi, was developed to maintain potency against multiple TRK kinase domain mutations.

Methods: Patients (pts) received LOXO-195 via a Phase I study (NCT03215511, n=20) or FDA expanded access single patient protocol (SPP, n=11). Eligible pts were ≥4-weeks old with a locally identified TRK fusion and had progressed or were intolerant to at least 1 priorTRKi. Parallel 3+3 dose escalations were pursued in adults and children, with intra-patient dose escalation permitted based on tolerance and pharmacokinetics. Pts aged <12 received BSA-adjusted doses.

Results: As of 03-DEC-2018, a total of 31 TRK-fusion pts (7 children, 24 adults) with 11 cancer types had been treated. Median duration on last prior TRKi was 9.5 months (range, 2-30). In the Phase 1, doses of 32 mg QD to 150mg BID were explored, and TEAEs (all grades/cause, in >3 pts) were dizziness/ataxia (65%), nausea/vomiting (50%), anemia (30%), myalgia, abdominal pain, fatigue, & lymphopenia (all 20%). Five Phase I pts (all adults) had DLTs: ataxia/dizziness (4), and ataxia/vomiting (1). For the SPPs: 1 pt dose-reduced and none discontinued for a TEAE. Cmax at doses ≥50 mg exceeded the predicted IC50 for TRK kinase mutations. Pretreatment tissue and/or plasma, as available, defined TRK kinase mutation status. Preliminary efficacy overall, and by TRK kinase mutation status, is shown in the Table.

Discussion: LOXO-195 had preliminary efficacy in pts with resistance to prior TRKi mediated by TRK kinase mutations. The subset of pts who develop TRK-independent resistance are unlikely to benefit from LOXO-195. Dose selection is ongoing in both children and adults.

Confirmed best overall response, all dose levels, investigator assessed per RECIST 1.1 (n=29≠)Patient CohortTotal Patients,nCR/PR, nStable Disease, nPD, nNon- evaluable, †nORRTRK Kinase Mutation20963245% (9/20)Solvent Front14742150% (7/14)Gatekeeper4111125% (1/4)xDFG2110050% (1/2)Identified bypass300210% (0/3)Other/ Unknown*61#31117% (1/6)Overall291096434% (10/29)≠ 2 pts still on study drug and awaiting 1st response assessment not included in Table.† 4 pts non-evaluable: 1 discontinued drug for unrelated new cancer diagnosis <28 days after start of study drug and 3 withdrew within 14 days of study drug start.* Includes 1 pt with no identified TRK kinase resistance mutationor bypass alteration# and 5 pts who could not be tested.# Pt intolerant but not resistant to prior TRKi

Citation Format: David Hyman, Shivaani Kummar, Anna Farago, Birgit Geoerger, Morten Mau-Sorensen, Matthew Taylor, Elena Garralda, Ramamoorthy Nagasubramanian, Michael Natheson, Lucy Song, Michael Capra, Mette Jorgensen, Alan Ho, Neerav Shukla, Steve Smith, Xin Huang, Brian Tuch, Nora Ku, Theodore W. Laetsch, Alexander Drilon, David Hong. Phase I and expanded access experience of LOXO-195 (BAY 2731954), a selective next-generation TRK inhibitor (TRKi) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT127.

Abstract 4736: Dose optimization of olaparib plus temozolomide in small cell lung cancer (SCLC) patient-derived xenograft (PDX) models for clinical translation

Introduction: SCLC is an aggressive high-grade neuroendocrine malignancy in which targeting DNA-damage repair pathways has shown efficacy in pre-clinical and clinical contexts. We previously conducted a phase I/II trial combining the PARP inhibitor olaparib (O) tablets with the alkylating agent temozolomide (T) in patients with relapsed SCLC, in which O and T were both given days (d) 1-7 of each 21 d cycle. The recommended phase 2 dose (RP2D) was O 200 mg PO BID and T 75 mg/m2 PO daily, and the response rate among the first 29 evaluable patients was 41.4%, with the primary toxicities being hematologic (Farago et al., ASCO 2018). Continuous PARP inhibition with O may improve efficacy, though it is unknown how best to incorporate T onto this backbone. Simultaneous clinical testing of multiple dosing schedules for concurrent OT would be impractical. Here we present an optimization of the OT regimen using PDX models generated from patients treated with OT. Methods: SCLC PDX models derived from two patients prior to their durable responses to OT, MGH1518-1B and MGH1528-1, were used for dose optimization. Based on a human-murine comparison of serum Cmax for OT, the estimated murine-equivalents for the RP2D doses were O 25 mg/kg BID and T 6.25 mg/kg/d. The RP2D regimen was then modulated in both dose intensity and duration in a 9-arm PDX trial. The arms included 3 schedule categories, with doses varied within each category: discontinuous regimens (OT d 1-7); continuous O regimens (O d1-21 + T d 1-7); and rapid- or slow-alternating regimens administering O and T on non-overlapping days. Tumor bearing mice were treated when subcutaneous tumors reached a volume of 400-800 cc, enabling measurement of tumor regression (PDX response) and time to volume doubling (PDX TTP). Findings: The RP2D regimen resulted in near-complete response in both models. This degree of regression was recapitulated with nearly all dosing schedules, and was not improved by increasing T to 2x-RP2D. However, the PDX TTP varied. In both models, the longest TTP was seen with continuous O at full- or half-RP2D and d 1-7 T at half-RP2D. This regimen prolonged TTP by 12% in MGH1518-1B and 20% in MGH1528-1, versus discontinuous OT at RP2D. Based on these results, we initiated clinical treatment in a new cohort of patients on OT, with a phase 1 dose escalation starting with O 50 mg BID d 1-21 and T 50 mg/m2 d 1-7 of each 21 d cycle (NCT02446704). At this first dose level, a partial response by RECIST 1.1 criteria was observed in a heavily pre-treated patient, indicating clinical activity of this combination with this new dosing strategy. Conclusions: In PDX models sensitive to OT at our previously determined RP2D, we find that continuous O with intermittent T permits dose reduction of both O and T without loss of efficacy. A clinical trial is ongoing to determine whether this strategy may enable longer-term dosing and improve efficacy in patients.

Citation Format: Benjamin J. Drapkin, Sarah Phat, David T. Myers, Jun Zhong, Beow Y. Yeap, Elisabetta Leo, Anna Stansiszewska, Aaron Smith, Elaine Cadogan, Maria C. Pietanza, Nicholas J. Dyson, Anna Farago. Dose optimization of olaparib plus temozolomide in small cell lung cancer (SCLC) patient-derived xenograft (PDX) models for clinical translation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4736.

Abstract 381: Combined inhibition of Bcl-2 and MCL-1 in small cell lung cancer (SCLC) is most effective in tumors with low Bcl-xL expression

Introduction: SCLC is an aggressive high-grade neuroendocrine malignancy in which targeting anti-apoptotic regulators such as Bcl-2 and Bcl-xL has shown efficacy in pre-clinical models but has not resulted in successful clinical trials (Rudin et al., Clin Cancer Res. 2012). Although SCLC cell-lines do not reflect the clinical impact of these inhibitors, patient-derived xenograft (PDX) models may more accurately recapitulate Bcl-2 family expression profiles and BH3 mimetic efficacy. One promising hypothesis is that the fellow anti-apoptotic protein MCL-1 rescues viability in the presence of Bcl-2/Bcl-xL antagonists. Here we evaluate the efficacy of the MCL-1 inhibitor S63845 in combination with a novel specific inhibitor of Bcl-2, BCL201/S55746, in SCLC patient-derived xenografts. Methods: BH3 mimetic compounds were tested for synergy in vitro in SCLC cell lines. A set of ten cell lines was chosen based on relative expression of BCL2, MCL1, and BCL2L1 (Bcl-xL) mRNA. Single agent and and pair-wise combinations of Bcl2 family inhibitors were compared in three-day growth inhibition assays. Loewe synergy scores were plotted versus Bcl2 family mRNA expression to identify the determinants of drug sensitivity. Based on the cell line synergy assays, a combination of BCL201/S55746 and S63845 was selected to test in PDX models of SCLC. Bcl-2 family expression was profiled across a panel of 37 SCLC PDX models generated at MGH by quantitative western blot, and standardized to the most sensitive SCLC cell line, NCI-H211. Ten models were selected based on absolute expression of Bcl-2, Bcl-xL and MCL-1. Mice were treated when subcutaneous tumors reached a volume of 400-800 cc, enabling precise measurement of tumor regression and time to tumor regrowth. Findings: Bcl-2 family dependency in SCLC cell lines was profiled with selective inhibitors as single agents or combinations. Maximum synergy was found between BCL201/S55746 and S63845 in cell lines with the highest Bcl-2:Bcl-xL expression ratio. Bcl-2 family expression was profiled across a panel of 37 PDX models of SCLC, and a representative set of 10 models was selected for in vivo testing. Consistent with cell line results, the two most sensitive models to BCL201/S55746+S63845 demonstrated the highest Bcl-2:Bcl-xL ratios, with moderate to high expression of MCL-1. In these models BCL201/S55746+S63845 resulted in a 44-70% tumor regression that was stable throughout 4 weeks of treatment. Efficacy was not dependent on MCL-1 expression, and was not strongly correlated with PDX sensitivity to platinum-etoposide. Conclusions: Combined inhibition of Bcl-2 with BCL201 and MCL-1 with S63845 is effective in SCLC tumors with relatively low Bcl-xL expression. This combination overcomes MCL-1 mediated resistance to Bcl-2 inhibitors, and represents a promising strategy to target anti-apoptotic dependency in SCLC.

Citation Format: Benjamin J. Drapkin, Sneha Sanghavi, David T. Myers, Jun Zhong, Sarah Phat, Youzhen Wang, Ensar Halilovic, Javad Golji, Anna Farago, Erick Morris, Nicholas J. Dyson. Combined inhibition of Bcl-2 and MCL-1 in small cell lung cancer (SCLC) is most effective in tumors with low Bcl-xL expression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 381.

What hides behind the MASC: clinical response and acquired resistance to entrectinib after ETV6-NTRK3 identification in a mammary analogue secretory carcinoma (MASC)

Here, we describe the dramatic response of a patient with an ETV6-NTRK3-driven mammary analogue secretory carcinoma to treatment with a pan-Trk inhibitor, and the development of acquired resistance linked to a novel NTRK3 mutation that interferes with drug binding. This case emphasizes how molecular profiling can identify therapies for rare diseases and dissect mechanisms of drug resistance.

Background

Mammary analogue secretory carcinoma (MASC) is a recently described pathologic entity. We report the case of a patient with an initial diagnosis of salivary acinic cell carcinoma later reclassified as MASC after next-generation sequencing revealed an ETV6-NTRK3 fusion.

Patients and methods

This alteration was targeted with the pan-Trk inhibitor entrectinib (Ignyta), which possesses potent in vitro activity against cell lines containing various NTRK1/2/3 fusions.

Results

A dramatic and durable response was achieved with entrectinib in this patient, followed by acquired resistance that correlated with the appearance of a novel NTRK3 G623R mutation. Structural modeling predicts that this alteration sterically interferes with drug binding, correlating to decreased sensitivity to drug inhibition observed in cell-based assays.

Conclusions

This first report of clinical activity with TrkC inhibition and the development of acquired resistance in an NTRK3-rearranged cancer emphasize the utility of comprehensive molecular profiling and targeted therapy for rare malignancies (NCT02097810).

Gene expression profiling reveals progesterone-mediated cell cycle and immunoregulatory roles of Hoxa-10 in the preimplantation uterus

Human infertility and recurrent pregnancy loss caused by implantation defects are poorly understood. Hoxa-10-deficient female mice have severe infertility and recurrent pregnancy loss due to defective uterine implantation. Gene expression profiling experiments reveal that Hoxa-10 is an important regulator of two critical events in implantation: stromal cell proliferation and local immunosuppression. At the time of implantation, Hoxa-10 mediates the progesterone-stimulated proliferation of uterine stromal cells. Hoxa-10 mutants express a stromal cell proliferation defect that is accompanied by quantitative or spatial alterations in the expression of two cyclin-dependent kinase inhibitor genes, p57 and p15. Hoxa-10 deficiency also leads to a severe local immunological disturbance, characterized by a polyclonal proliferation of T cells, that occurs in place of the normal progesterone-mediated immunosuppression in the periimplantation uterus.

Inhibition of DNA binding by the phosphorylation of poly ADP-ribose polymerase protein catalysed by protein kinase C

Purified type II (beta) and type III (alpha) protein kinase C phosphorylates highly purified polyADP-ribose polymerase in vitro whereby 2 mols of phosphate are transferred from ATP to serine and threonine residues present in the 36 and 56 kDa polypeptide domains of the polymerase protein. Calf thymus DNA was a non-competitive inhibitor of the protein kinase C catalyzed phosphorylation of polyADP-ribose polymerase. Coincidental with the phosphorylation of the protein the polymerase activity and DNA binding capacity of polyADP-ribose polymerase were inhibited. These in vitro findings may have possible cell biological significance in cellular signal transduction.

Protein kinase C in transmembrane signalling

Protein kinase C functions as the transducer of a second messenger, diacylglycerol, and is the major receptor for tumour-promoting phorbol esters. The enzyme is a family of proteins with closely but distinct structures and individual enzymological properties. Members of the family are differently distributed in particular cell types and limited intracellular locations from lower organisms to mammalian tissues. The enzyme appears to interact with many signalling pathways, and display functions in the processing and modulation of cellular responses to external stimuli. Presumably, each member of the family plays discrete roles in the control of a variety of membrane functions and activation of gene transcription.

The phosphorylation site of Ca(2+)-dependent protein kinase from alfalfa

A 50 kDa, calcium-dependent protein kinase (CDPK) was purified about 1000-fold from cultured cells of alfalfa (Medicago varia) on the basis of its histone H1 phosphorylation activity. The major polypeptide from bovine histone H1 phosphorylated by either animal protein kinase C (PK-C) or by the alfalfa CDPK gave an identical phosphopeptide pattern. The phosphoamino acid determination showed phosphorylation of serine residues in histone H1 by the plant enzyme. Histone-related oligopeptides known to be substrates for animal histone kinases also served as substrates for the alfalfa kinase. Both of the studied peptides (GKKRKRSRKA; AAASFKAKK) inhibited phosphorylation of H1 histones by bovine and alfalfa kinases. The results of competition studies with the nonapeptide (AAASFKAKK), which is a PK-C specific substrate, suggest common features in target recognition between the plant Ca(2+)-dependent kinase and animal protein kinase C. We also propose that synthetic peptides like AAASFKAKK can be used as a tool to study substrates of plant kinases in crude cell extracts.