Efficacy and safety of larotrectinib in pediatric patients with tropomyosin receptor kinase (TRK) fusion-positive cancer: An expanded dataset

10030

Background: Neurotrophic tyrosine receptor kinase ( NTRK) gene fusions are oncogenic drivers in various tumor types across all ages. Larotrectinib is a first-in-class, central nervous system (CNS)-active, highly selective tropomyosin receptor kinase (TRK) inhibitor approved for pediatric and adult patients (pts) with TRK fusion-positive cancer, demonstrating an objective response rate (ORR) of 88% across 78 pediatric pts with non-CNS cancers (van Tilburg et al, SIOP 2021). We report an analysis of the efficacy and safety of larotrectinib in an expanded dataset of pediatric pts with TRK fusion-positive cancer. Methods: Pediatric pts (< 18 years) with non-CNS TRK fusion-positive cancer in larotrectinib clinical trials (NCT02637687, NCT02576431) were included and ORR (RECIST v1.1) was investigator (INV)-assessed. Data cut-off was July 20, 2021. Results: A total of 94 pts were included in this analysis. Tumor types included infantile fibrosarcoma (52%), other soft tissue sarcoma (40%), congenital mesoblastic nephroma (2%), thyroid cancer (2%), bone sarcoma (1%), breast cancer (1%), and melanoma (1%). Pts had gene fusions involving NTRK1 (43%), NTRK2 (3%), or NTRK3 (54%). Median age was 2.2 years (range 0–18 years). Of the 62 (66%) pts who received prior systemic therapy, 32 (52%) received ≥2 lines. The INV-assessed best ORR for the 93 evaluable pts was 84% (95% confidence interval [CI] 75–91): 35 (38%) complete response (CR; including two pending confirmation and 10 pathological CR), 43 (46%) partial response (two pending confirmation), 11 (12%) stable disease, two (2%) progressive disease, and two (2%) not determined. The median time to response was 1.8 months. Overall, median duration of response was 43.3 months (95% CI 23.4–NE); median follow-up was 26.0 months. Median progression-free survival and overall survival (OS) were 37.4 months (95% CI 22–NE) and not reached, respectively; median follow-up was 21.2 and 30.3 months, respectively. The 36-month OS rate was 93% (95% CI 86–99). Treatment duration ranged from 1+ to 63+ months. At data cut-off, 31 pts had progressed; 18 continued treatment post-progression for ≥4 weeks. There were no treatment-related deaths. Treatment-related adverse events (TRAEs) occurred in 81% of pts (23% were Grade [G] 1, 28% G2, 25% G3, and 5% G4). The most common TRAE was increased aspartate aminotransferase (31 pts [33%]). Four pts (4%) discontinued treatment due to TRAEs. Neurological TRAEs occurred in 12% of pts (5% were G1, 4% G2, and 2% G3). The most common neurological TRAE was headache (5 pts [5%]). Conclusions: In this expanded dataset, larotrectinib continues to demonstrate rapid and durable tumor-agnostic efficacy, extended survival, and a favorable safety profile in pediatric pts with TRK fusion-positive cancer. These results highlight the importance of identifying NTRK gene fusions in pediatric solid tumors. Clinical trial information: NCT02576431, NCT02637687.

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.

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.

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.

Phase I results of the INFORM2 combination study of nivolumab and entinostat in children and adolescents: INFORM2 NivEnt

10034

Background: Pediatric patients with relapsed or refractory high-risk solid and CNS tumors have dismal survival. To date treatment with immune checkpoint inhibitors in this population has been disappointing. This study exploits the immune enhancing effects of entinostat on nivolumab in biomarker enriched subpopulations. The study aims to determine the pediatric recommended phase II dose (pRP2D) and to evaluate activity and safety. Methods: This is an exploratory non-randomized, open-label, multinational seamless phase I/II trial in children and adolescents with relapsed / refractory or progressive high-risk solid and CNS tumors. The phase I is divided in 2 age cohorts: 12–21 years (y) and 6–11y and follows a 3 + 3 design with two dose levels for entinostat (dose level 1: 2 mg/m2 and dose level 2: 4 mg/m2 once per week) and fixed dose nivolumab (3 mg/kg every 2 weeks). Patients entering the trial on pRP2D can seamlessly enter phase II which consists of a biomarker defined four group basket trial: high mutational load (group A), high PD-L1 mRNA expression (group B), focal MYC(N) amplification (group C), low mutational load and low PD-L1 mRNA expression and no MYC(N) amplification (group D). Results: The first patient was enrolled in May 2020 and at the time of the data cut (21-JAN-2022), 19 patients were treated. The median age at enrollment was 14 y. In the 12 – 21y cohort 15 patients were enrolled and four patients in the 6 – 11y cohort. The most frequent treatment-related AEs to date were thrombocytopenia in six (32%), nausea and vomiting both in four (21%), and neutropenia in three patients (16%). Five patients (26%) experienced grade 3/4 mostly reversible treatment-related AEs, e.g. neutropenia/leukopenia. No treatment related deaths were reported. In the 6 – 11y cohort dose escalation is ongoing. In the 12 – 21y cohort, one DLT (CTCAE grade 3 thrombocytopenia) was observed in six patients on dose level two, which was determined as the pRP2D of the combination. At the time of the data cut, 10 patients (six in arm D and four patients in which the biomarker group was not yet determined) had received at least one RECIST/RANO response evaluation by central review in phase II. One patient (17%) in arm D with metastatic relapsed renal cell carcinoma (RCC) harboring a typical PRCC-TFE3 fusion showed a PR after two cycles and finally achieved an ongoing CR. Extensive explorative analyses of immune signatures derived from INFORM RNA-Seq and WES data revealed that both the primary diagnosis and the current relapse samples harbored a remarkable high immune cell infiltration, especially CD8+ T-cells. Conclusions: The first and ongoing global INFORM2 trial has identified the pRP2D for the nivolumab and entinostat combination in the older age cohort with good tolerability. A patient with metastasized relapsed RCC experienced a CR. The role of immune infiltration as a potential predictive biomarker is currently being explored. Clinical trial information: NCT03838042.

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.

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.

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.

The pediatric precision oncology study INFORM: Clinical outcome and benefit for molecular subgroups

LBA10503

Background: Several pediatric precision oncology programs have identified molecular actionable variants. However, the clinical benefit is largely unknown. We here report a target prioritization algorithm and associated clinical outcome. Methods: INFORM is a prospective, non-interventional, multi-center, multi-national, and feasibility registry collecting clinical and molecular data. Patients with refractory/relapsed/progressive malignant disease, including primary diagnosis high-risk entities, can be enrolled. Fresh frozen tumor material (incl. germline DNA) was subjected to WES, lcWGS, RNA-Seq, RNA expression array and DNA-methylation. A weekly interdisciplinary molecular board reviewed and prioritized alterations based on a 7- step scale from ‘very high’ to ‘very low’, depending on the type of alteration and its entity specific relevance (described by Worst et al. Eur J Cancer 2016). Results: To date, more than 1300 patients were enrolled. 525 patients finished follow-up and were included in this analysis. They were enrolled in 72 centers in 8 countries. The median age was 12.0 (range 0 - 40) years. Average turnaround time from submission to report was 25.4 days. Median PFS and OS were 116 (95% CI 105 – 135) and 289 (95% CI 250 – 335) days. The distribution of the highest priority target per patient was: very high 8.0%, high 14.8%, moderate 20.3%, intermediate 23.6%, borderline 14.4%, low 2.5%, very low 1.0% and no actionable target 15.4%. 149 patients received targeted treatment on the basis of identified targets, of which 20 had a very high priority target (mostly ALK, BRAF and NRAS mutations and MET and NTRK-fusions) with a median PFS of 204.5 (95% CI 91.0 – 628.0) compared to 114 (95% CI 103 – 133) days in all other 505 patients (p = 0.0095). OS did not show clinically relevant differences. Explorative analysis of the time to progression (TTP) ratio (before compared to after enrollment) showed that patients treated according to a very high priority target had a higher TTP ratio (1.0) compared to all other patients (0.7). Possible predisposition syndromes were identified in 7.8% of patients, half of which were newly diagnosed. Methylation analysis provided a diagnosis refinement in 8% of CNS tumors. Conclusions: Pediatric precision oncology in a real world, multi-national setting is feasible. The prioritization algorithm identifies subgroups benefitting from molecularly matched targeted treatment. Still, for the patients without a very high priority target further layers of molecular and functional data should be incorporated in future programs.

INFORM2 exploratory multinational phase I/II combination study of nivolumab and entinostat in children and adolescents with refractory high-risk malignancies: INFORM2 NivEnt

TPS10065

Background: Immune checkpoint inhibition in children has shown limited success rates until now. This is most likely due to the fact that the vast majority of pediatric cancers are so-called immunologic cold tumors, and that patients have been enrolled in an unselected manner in single agent trials. Recently, it has been shown that the class I selective HDAC inhibitor entinostat has significant immune enhancing activity in vitro and in vivo. This is mediated through multiple mechanisms including depletion of myeloid-derived suppressor cells, activation of neoantigen transcription and increase of MHC expression. Methods: INFORM2 NivEnt is an exploratory nonrandomized, open-label, multinational and multicenter seamless phase I/II basket trial of nivolumab and entinostat in children and adolescents with relapsed, refractory or progressive high-risk solid and CNS tumors. Patients aged 6-21 will be allocated to the following biomarker-defined groups: high mutational load ( > 100 somatic SNVs/exome; group A), high PD-L1 mRNA expression (RPKM > 3; group B), focal MYC(N) amplification (group C), low mutational load and low PD-L1 mRNA expression and no MYC(N) amplification (Biomarker low group D). Phase I determines the recommended phase 2 dose for the combination for the age groups 6-11 and 12-21 years. Patients will receive nivolumab 3mg/kg every 2 weeks. Entinostat has 2 dose levels: 2mg/m2 and 4mg/m2 once per week. Patients can seamlessly enter the phase II which investigates activity (defined as best response during the first 6 cycles) in the 4 biomarker groups A-D. The duration of treatment is 12 cycles, preceded by 1 entinostat priming week. Interim analyses for futility will be performed after every 10 patients in each group. The study will enroll a maximum of 128 patients in Germany, The Netherlands, Sweden, France, Australia and additional countries under discussion. A comprehensive accompanying biomarker program will investigate a series of immune and epigenetic pharmacodynamic biomarkers. Clinical trial information: NCT03838042.

Larotrectinib efficacy and safety in pediatric TRK fusion cancer patients

10010

Background: TRK fusions involving NTRK1, NTRK2, and NTRK3 genes have been identified in a broad range of pediatric and adult malignancies. Larotrectinib, a highly-selective oral TRK inhibitor, was well tolerated and showed encouraging antitumor activity in 17 pediatric patients (pts) with TRK fusion cancer (Laetsch et al, Lancet Oncol 2018). Here, we present data on the clinical efficacy and safety of larotrectinib in 38 pediatric pts with TRK fusion cancer from an expanded dataset. Methods: Pediatric pts enrolled in two larotrectinib clinical trials (NCT02637687, NCT02576431) with TRK fusion cancer detected by local testing were included; pts with primary CNS tumors were excluded from this report. Larotrectinib was administered until complete surgical resection, disease progression, withdrawal, or unacceptable toxicity. Disease status was investigator-assessed using RECIST v1.1. Data cutoff: July 30, 2018. Results: As of July 30, 2018, 38 children and adolescents < 18 y with TRK fusion cancer were enrolled. Median age was 2.3 y (range 0.1–14.0); 14 (37%) were < 1 y. 18 (47%) had infantile fibrosarcoma, 15 (39%) other soft tissue sarcoma, 2 (5%) thyroid cancer and 1 (3%) each had gastrointestinal stromal tumor, melanoma, or mesoblastic nephroma. TRK fusions involved NTRK1, 2, and 3 in 18 (47%), 2 (5%), and 18 (47%) pts, respectively. Half of the pts had metastatic disease and half locally advanced disease at entry. 26 pts (68%) had received prior systemic therapy (median lines: 1 [range 0–4]) and 6 were treatment-naïve. In 34 evaluable pts, the overall response rate was 94%: 12 CRs, 18 confirmed PRs, and 2 PRs pending confirmation; 2 had stable disease. Median duration of response had not been reached (range 1.6+ to 26.7+ months); 84% > 1 y. At data cutoff, 28 pts (74%) remained on treatment; 4 pts discontinued due to complete surgical resection and 4 due to disease progression while on therapy, 2 of whom initially responded (PR). Adverse events were mostly grade 1–2. Conclusions: Larotrectinib treatment resulted in a high and durable response rate in pediatric pts with TRK fusion cancer together with a favorable safety profile. Routine testing for NTRK gene fusions in pediatric cancer pts is recommended in the appropriate clinical context. Clinical trial information: NCT02637687 and NCT02576431.

Activity of larotrectinib in TRK fusion cancer patients with brain metastases or primary central nervous system tumors

2006

Background: TRK fusions are oncogenic drivers of a variety of cancers, many of which can involve the central nervous system (CNS). Larotrectinib is an FDA-approved selective TRK inhibitor for the treatment of TRK fusion cancer (Drilon et al, NEJM 2018). While larotrectinib has been shown to cross the blood–brain barrier (Ziegler et al, Br J Cancer 2018), its clinical activity in a series of TRK fusion cancers with primary or metastatic intracranial disease has not been described. Methods: Patients (pts) with non-primary CNS solid tumors with brain metastases, or primary CNS tumors harboring a TRK fusion treated with larotrectinib in 2 clinical trials (NCT02637687, NCT02576431) were identified. Larotrectinib was administered until disease progression (PD), withdrawal, or unacceptable toxicity. Disease status was investigator-assessed (RANO and RECIST). Data cutoff: July 30, 2018. Results: 14 pts were identified: 5 non-primary CNS solid tumors (3 lung cancer, 2 thyroid cancer; fusion type: 2 ETV6-NTRK3, 2 SQSTM1-NTRK3, 1 EPS15-NTRK1; age range 25–79 y) and 9 primary CNS tumors (3 glioma, 2 glioblastoma, 1 astrocytoma, 3 NOS; fusion type: 3 BCR-NTRK2, 2 KANK-NTRK2, 1 each of AFAP1-NTRK1, AGTPBP1-NTRK2, ETV6-NTRK3, SPECC1L-NTRK2; age range 2–79 y). In the 5 pts with non-primary CNS tumors, the best objective response to therapy was PR in 3 (60%, 1 pending confirmation), SD in 1 (20%), and not evaluable (NE) in 1 (20%). Duration of response ranged from 9+ to 13 mo. In the 9 pts with primary CNS tumors, disease control was achieved in all evaluable pts (primary PD not observed; 1 pt required dose increase). The best objective response to therapy was PR in 1 (11%; pending confirmation, −55% tumor shrinkage, ongoing at 3.7 mo), SD in 7 (78%; tumor shrinkage range −1% to −24% for pts with measurable disease, 5 had SD > 4 mo), and NE in 1 (11%). Duration of treatment ranged from 2.8–9.2+ mo. Conclusions: Larotrectinib is active in pts with TRK fusion cancers with intracranial disease. Confirmed responses and durable disease control were seen in metastatic disease and primary CNS tumors of various histologies. These results further support expanded testing for TRK fusions across all cancers, including primary CNS tumors. Clinical trial information: NCT02637687 and NCT02576431.

A phase I study of LOXO-292, a highly selective RET inhibitor, in pediatric patients with RET-altered cancers

TPS10066

Background: Genomic alterations in the RET kinase, including gene fusions and activating point mutations, are implicated in the pathogenesis of lung, thyroid, sarcoma and other cancers in both chidren and adults. Currently available multikinase inhibitors with anti-RET activity are non-selective and may be associated with less favorable toxicity profile. LOXO-292 is a novel, highly selective, ATP-competitive small molecule RET inhibitor. LOXO-292 has preclinical nanomolar potency against diverse RET alterations (e.g. fusions, activating mutations and anticipated acquired resistance mutations) and anti-tumor activity in the brain. LOXO-292 has demonstrated clinical activity in adult patients with RET-alterated solid tumors. Methods: LIBRETTO-121 (EudraCT 2019-000212-28) is an ongoing multicenter phase 1/2 dose escalation multicenter trial in patients 6 months-21 years of age with advanced, RET-altered solid and CNS tumors. Dose escalation follows a rolling 6 design starting at the equivalent of the adult recommended phase 2 dose. Enrollment began on 12 Feb 2019 and is ongoing. Key eligibility criteria include: solid or CNS tumor with a documented RET gene alteration refractory to standard therapy; age 6 months to 21 years of age; and adequate bone marrow, liver and kidney function. LOXO-292 is administered orally BID for continuous 28-day cycles. Both capsule and liquid suspension dosage forms are available. The primary objective of the phase 1 portion of the study is to determine safety and dose limiting toxicities. Key secondary objectives include characterization of pharmacokinetic properties, identification of the MTD and initial characterization of the anti-tumor activity of LOXO-292. Archival tissue will be used to further characterize molecular abnormalities. Clinical trial information: 2019-000212-28.