Kinase Fusion Gene Research Articles

HGG-18. Long-term efficacy and safety of larotrectinib in paediatric patients with tropomyosin receptor kinase (TRK) fusion-positive primary central nervous system (CNS) tumours

INTRODUCTION: Neurotrophic tyrosine receptor kinase (NTRK) gene fusions are oncogenic drivers in various tumours. Larotrectinib, a highly selective TRK inhibitor, demonstrated an objective response rate (ORR) of 75% across 206 evaluable patients with various non-primary CNS cancers (Hong et al, ASCO 2021). We report long-term data on larotrectinib-treated paediatric patients with TRK fusion-positive primary CNS tumours. METHODS: Patients aged <18 years with TRK fusion-positive primary CNS tumours enrolled in two clinical trials (NCT02637687, NCT02576431) were included. Larotrectinib was administered at 100 mg/m2 (maximum: 100 mg) twice-daily. Response was investigator-assessed per RECIST v1.1 and RANO. RESULTS: As of July 2021, 28 patients with TRK fusion-positive primary CNS tumours were enrolled, including 14 high-grade and eight low-grade gliomas. Median age at enrolment was 7.0 years (range 1.0–17.0). Twenty-three patients (82%) received prior systemic therapy and 12 (43%) received prior radiotherapy. The ORR was 39% (95% confidence interval [CI] 22–59): three complete responses, eight partial responses, 15 stable disease and two progressive disease. The 24-week disease control rate was 82% (95% CI 63–94). Median duration of response (DoR) was not reached; median follow-up was 25.6 months. Median progression-free survival was 21.9 months (95% CI 9.2–not estimable). Median overall survival (OS) was not reached; median follow-up was 27.6 months. DoR and OS 24-month rates were 53% and 71%, respectively. Treatment duration ranged from 1.0 to 39.0+ months. Treatment-related adverse events (TRAEs) were mostly Grade 1–2. Grade 3–4 events occurred in three patients (increased gamma-glutamyltransferase, hyperglycaemia, hypernatraemia, hyponatraemia and neutropaenia). No patients discontinued treatment due to TRAEs. Fourteen patients progressed on treatment; four continued treatment post-progression for ≥4 weeks. CONCLUSION: Larotrectinib demonstrated high disease control rate, durable responses and a manageable safety profile. These results support testing for NTRK gene fusions in paediatric patients with primary CNS tumours.

HGG-21. Oncogenic tyrosine kinase gene fusions in infant-type hemispheric gliomas - comparison of RNA- and DNA-based methods for their reliable detection

High-grade diffuse gliomas (HGG) in early childhood are characterized by a more favorable outcome compared to older children. We demonstrated in previous studies that these tumors have stable genomes. Activating tyrosine kinase gene fusions in infant-type hemispheric gliomas represent therapeutic targets. 50 supratentorial HGG occurring in children younger than four years were retrieved from the archives of the Brain Tumor Reference Center, Institute of Neuropathology, Bonn University. DNA and RNA were extracted from FFPE tumor samples. Gene fusions were identified on the DNA level by FISH using break-apart probes for ALK, NTRK1, -2, -3, ROS1 and MET and Molecular Inversion Probe (MIP) methodology. On the RNA level, fusion transcripts were detected by targeted RNA sequencing as well as Nanostring assay with fusion-specific probes. 37 supratentorial HGG occurred in the first year of life, 13 HGG between one and four years. 18 cases showed fusions of ALK to different partners; all occurred in the first year of life (18/37, 48.6%). Fusions of ROS1 were found in 5, MET in 3, NTRK1, -2, -3 in 10 cases. 12 cases showed no and two cases novel fusions. The different methods led to comparable results. Only recurrent fusions with known fusion partners were detectable with fusion sequence-specific Nanostring probes and library construction for targeted RNA sequencing failed in a fraction of cases. Break-apart FISH led to reliable results on the next day, and MIP technology represented the most sensitive method for analysis of FFPE samples. Gene fusions involving the tyrosine kinase genes ALK, MET, ROS1 and NTRK1, -2, -3 occurred in 72% of HGG of young children; most frequent were ALK fusions occurring in tumors of infants. DNA-based MIP technology represented the most robust and sensitive assay. A combination of RNA- and DNA-based methods to detect these fusions with high reliability is recommended.

Precision Medicine in Cholangiocarcinoma: Past, Present, and Future.

Cholangiocarcinoma (CCA), or biliary tract cancer, has a poor prognosis. The median survival time among patients with CCA is under 2 years from diagnosis, and the global 5-year survival rate is only 10%. First-line therapy with chemotherapeutic agents, gemcitabine plus cisplatin, has traditionally been used to treat unresectable advanced CCA. In recent years, precision medicine has become a mainstream cancer treatment due to innovative next-generation sequencing technology. Several genetic alterations, including mutations, gene fusions, and copy number variations, have been found in CCA. In this review, we summarized the current understanding of genetic profiling in CCA and targeted therapy in CCA. Owing to the high heterogeneity of CCA, tumor microenvironmental factors, and the complexity of tumor biology, only pemigatinib, infigratinib, ivosidenib, larotrbctinib, and entrectinib are currently approved for the treatment of CCA patients with fibroblast growth factor receptor 2 gene (FGFR2) fusion, isocitrate dehydrogenase gene (IDH1) mutation, and neurotrophin receptor tyrosine kinase gene (NRTK) fusion, respectively. Additional targeted therapies, including other FGFR2 inhibitors, PI3K/AKT/mTOR inhibitors, and BRAF-directed targeted therapy, have been discussed for the management of CCA, and immune checkpoint inhibitors, particularly pembrolizumab, can be administered to patients with high microsatellite instability tumors. There is a further need for improvement in precision medicine therapies in the treatment of CCA and discuss the approved and potential targeted therapies for CCA.

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 &lt; 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 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.

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 (&lt; 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.

SO-31 Long-term efficacy and safety of larotrectinib in patients with tropomyosin receptor kinase (TRK) fusion gastrointestinal (GI) cancer: An expanded dataset

Neurotrophic tyrosine receptor kinase ( NTRK ) gene fusions are oncogenic drivers in various tumour types. Larotrectinib is a first-in-class, highly selective tropomyosin receptor kinase (TRK) inhibitor approved for use in adult and paediatric patients with TRK fusion cancer, demonstrating an objective response rate (ORR) of 41% across 18 patients with gastrointestinal (GI) cancer (Boni et al, WCGI 2021). We report an updated analysis from an expanded dataset of patients with TRK fusion GI cancer with longer follow-up. Patients with TRK fusion GI cancer treated with larotrectinib in the phase II clinical trial NAVIGATE (NCT02576431) were included in this analysis. Responses were investigator-assessed using RECIST v1.1. Data cut-off was 20 July 2021. As of data cut-off, 34 patients with metastatic TRK fusion GI cancer were enrolled. Median age was 63.5 years (range 32–90). The tumour types included were colorectal (CRC; n=19), pancreatic (n=6), cholangiocarcinoma (n=4), appendiceal (n=1), duodenal (n=1), gastric (n=1), hepatocellular carcinoma (n=1) and oesophageal (n=1). Among the patients with CRC, 10 were microsatellite instability high (MSI-H), seven were MSI-H not detected (including stable) and two were unknown. Overall, 32%, 35% and 18% of patients had received 1, 2, or ≥3 prior lines of systemic therapy, respectively. ORR in the 33 evaluable patients was 33% (95% confidence interval [CI] 18–52): one complete response (CR; 3%), 10 partial responses (PR; three pending confirmation [30%]), 15 stable disease (SD; 45%), four progressive disease (PD; 12%) and three not determined (ND; 9%). Median time to response was 1.9 months (range 1.7–5.0). Median duration of response (DoR) was 7.3 months (95% CI 3.5–27.3); median follow-up was 26.4 months. Median progression-free survival (PFS) was 5.4 months (95% CI 2.7–9.0); median follow-up was 5.4 months. Median overall survival (OS) was 12.5 months (95% CI 6.1–33.4); median follow-up was 7.7 months. In the 19 patients with CRC, ORR was 47% (95% CI 24–71): one CR (5%), eight PR (three pending confirmation [42%]), eight SD (42%), one PD (5%) and one ND (5%). Of the nine responders, six were MSI-H. The median DoR was not reliably estimable, but the 12-month rate was 67% (95% CI 29–100); median follow-up was 17.8 months. Median PFS was 5.5 months (95% CI 2.7–not estimable); median follow-up was 5.6 months. Median OS was 12.5 months (95% CI 6.1–36.5); median follow-up was 7.8 months. Treatment duration for all GI patients ranged from 0.2+ to 32.2+ months. At data cut-off, 14 patients had progressed; four continued treatment post-progression for ≥4 weeks. Treatment-related adverse events (TRAEs) occurred in 65% of patients (27% were Grade [G]1, 21% G2, 12% G3 and 6% G4). No patients discontinued treatment due to TRAEs. In this expanded dataset with longer follow-up, larotrectinib continues to demonstrate rapid, durable responses, extended survival and a favourable safety profile in patients with TRK fusion GI cancer, particularly in those with CRC. These results highlight the importance of identifying NTRK gene fusions in patients with GI cancer, particularly in those with MSI-H CRC.

Characterization of NTRK alterations in metastatic colorectal cancer.

e15569 Background: Increased molecular profiling ability has resulted in the recognition of important actionable genes that can be used to direct targeted therapies in colorectal cancers (CRC). Neurotrophin receptor tyrosine kinase (NTRK) gene fusions are one of these molecular alterations that are potentially actionable with novel targeted therapeutics. However, other biologically pathogenic NTRK alterations, including point mutations, are not yet actionable in CRC. This study aimed to characterize NTRK alterations, including fusions in metastatic CRC patients. Methods: Molecular characteristics of 917 patients with CRC were collected from the Moffitt Cancer Center Clinical Genomics Action Committee database. Demographic, clinicopathological, and molecular data and treatment history were abstracted from electronic medical records. Mutations with potential oncogenic activity are considered “potentially pathogenic”, while alterations with proven oncogenic activity such as fusions are considered “pathogenic”. Results: There were 917 patients with CRC from November 2013 to December 2021, and 77 of them had NTRK alterations excluding synonymous mutations (8.3%, 77/917). Six patients had potentially pathogenic NTRK alterations, including one NTRK rearrangement (0.6%, 7/917); however, only 1 patient had an actionable pathogenic NTRK1 fusion (0.1%, 1/917), while the others (70) were a variant of unknown significance (VUS). The majority of NTRK alterations were missense mutations (92%; 71/77). The NTRK1 fusion partner was LMNA and occurred in the setting of an MSI-H tumor (3.7%; 1/27). Among patients with pathogenic and potentially pathogenic alterations (N = 7), there was only 1(14%) patient who had low tumor mutation burden (TMB) (&lt; 10 mut/MB). Most patients were older than 50 years (70.1%, 54/77) and male (58.4%, 45/77). Thirty-six patients (46..7%) had right-sided tumor, while 41 patients (53.2%) left-sided. Across all NTRK alterations cohort, MSI-H was found in 10.3% (7/77), and POLE/POLD1 pathogenic mutations were seen in 6.4% (5/77) patients. Conclusions: NTRK gene fusion is a relatively rare event (&lt; 1%) in CRC, including the MSI-H subtype. The majority of NTRK alterations in CRC are VUS, and they are not actionable, and they tend to be seen in the tumors with high TMB (TMB &gt; 10). Hypermutator tumors cause frequent VUS alterations in the NTRK gene with unknown clinical relevance.

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 &lt; 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.

SO-32 Entrectinib in NTRK fusion-positive gastrointestinal cancers: Updated integrated analysis

Neurotrophic tyrosine receptor kinase ( NTRK ) gene fusions, coding for constitutively active chimeric tyrosine receptor kinase (TRK) proteins, are oncogenic drivers found in a large range of tumour types, including gastrointestinal cancers. Entrectinib is a potent TRK inhibitor with activity in the CNS, that has demonstrated deep and durable responses in patients with a range of NTRK fusion-positive solid tumours from the phase 1/2 ALKA-372-001 (EudraCT 2012-000148-88), STARTRK-1 (NCT02097810) and STARTRK-2 (NCT02568267) clinical trials.

Inhibition of EGFR and MEK surmounts entrectinib resistance in a brain metastasis model of NTRK1-rearranged tumor cells.

Tropomyosin receptor kinase (TRK) inhibitors have demonstrated histology‐agnostic efficacy in patients with neurotrophic receptor tyrosine kinase (NTRK) gene fusion. Although responses to TRK inhibitors can be dramatic and durable, duration of response may eventually be limited by acquired resistance via several mechanisms, including resistance mutations such as NTRK1‐G595R. Repotrectinib is a second‐generation TRK inhibitor, which is active against NTRK1‐G595R. However, its efficacy against entrectinib‐resistant tumors has not been fully elucidated. In the present study, we established entrectinib‐resistant tumor cells (M3B) in a brain metastasis model inoculated with NTRK1‐rearranged KM12SM cells and examined the sensitivity of M3B cells to repotrectinib. While M3B cells harbored the NTRK1‐G595R mutation, they were unexpectedly resistant to repotrectinib. The resistance was due to extracellular signal–regulated kinase (ERK) reactivation partially mediated by epidermal growth factor receptor (EGFR) activation. We further demonstrate that the triplet combination of repotrectinib, EGFR inhibitor, and MEK inhibitor could sensitize M3B cells in vitro as well as in a brain metastasis model. These results indicate that resistant mutations, such as NTRK1‐G595R, and alternative pathway activation, such as ERK activation, could simultaneously occur in entrectinib‐resistant tumors, thereby causing resistance to second‐generation inhibitor repotrectinib. These findings highlight the importance of intensive examinations to identify resistance mechanisms and application of the appropriate combination treatment to circumvent the resistance.

Impact of compound mutations I1171N + F1174I and I1171N + L1198H on the structure of ALK in NSCLC pathogenesis: atomistic insights

Anaplastic lymphoma kinase (ALK) fusion genes are found in 3%–5% of non-small cell lung cancers (NSCLCs). NSCLC is the most common type of lung cancer, accounting for 84% of all lung cancer diagnoses. Available treatment options for ALK-positive NSCLCs involve the use of ALK tyrosine kinase inhibitors (ALK-TKIs) which have shown to be effective with a high response rate. Nonetheless, the emergence of multiple compound mutations such as I1171N + F1174I or I1171N + L1198H has been reported to cause resistance to all approved ALK-TKIs. However, the underlying molecular mechanisms surrounding the impact of these compound mutants remain poorly understood. Hence, we performed molecular dynamics simulations to characterize the structural effects and functional implications of these compound mutations. Findings revealed a destabilizing effect on ALK by mutants as compared to the wild-type ALK structure. Also, further insights revealed a lower root-mean-squared fluctuation, radius of gyration, and solvent-accessible surface area values of I1171N + F1174I and I1171N + L1198H ALK compound mutations suggesting that the mutants have a more compact structure and a smaller surface area than the wild-type protein. The mutants also distorted the activation loop residues (Tyr1278, Tyr1282, and Tyr1283) in the ALK structure, which further identify them as possible disruptors of phosphorylation. In contrast to wild conformation, the mutant conformations exhibited a reduced node degree in their residue interaction networks. Collectively, our findings provide deeper insights into the deleterious effects of I1171N + F1174I and I1171N + L1198H ALK compound mutations, which may contribute to NSCLC pathogenesis. Communicated by Ramaswamy H. Sarma

Timing of NTRK Gene Fusion Testing and Treatment Modifications Following TRK Fusion Status Among US Oncologists Treating TRK Fusion Cancer.

Background Neurotrophic tyrosine receptor kinase (NTRK) gene fusions are oncogenic drivers with an estimated prevalence of less than 1% across all solid tumors. Tropomyosin receptor kinase inhibitors (TRKis) block the constitutively activated tyrosine receptor kinase (TRK) fusion protein produced in NTRK gene fusion positive (NTRK+) tumors from downstream signaling. Tropomyosin receptor kinase inhibitors are now first-line (1L) or subsequent treatment options for TRK fusion cancers.ObjectiveThis study assessed timing of NTRK gene fusion testing and treatment modifications among patients with TRK fusion cancers.Patients and MethodsThis was a one-time physician questionnaire with a retrospective, multisite patient chart abstraction of oncology practices in the USA. From June to September 2020, medical oncologists from the Oncology Provider Extended Network (OPEN) who treated patients with NTRK+ advanced/metastatic solid tumors abstracted information into electronic case report forms (eCRFs) for adult patients with advanced/metastatic solid tumors and a NTRK+ tumor test result with a known fusion partner. Use of NTRK testing in routine clinical practice among patients with advanced/metastatic solid tumors was assessed. Data included demographic, clinical, and NTRK gene fusion testing characteristics. Responses were summarized using descriptive statistics.ResultsTwenty-eight community-based medical oncologists who had managed or treated 148 patients with advanced/metastatic TRK fusion cancer between 01/01/2016 and 12/31/2019 completed the survey. Lung (27%), thyroid (18%), salivary gland (14%), and colorectal (12%) were the most commonly reported tumor types. A majority (68%) tested NTRK status prior to 1L initiation; testing after disease progression on 1L (36%), 2L (25%), and 3L (21%) was also noted. Most oncologists (96%) reported no difficulty interpreting NTRK reports. Nearly all (96%) indicated using next-generation sequencing (NGS) for determining NTRK status. The majority (57%) indicated that age, tumor type, and performance status did not impact NTRK testing decisions. Less than half (46%) include TRKi therapy following NTRK+ determination. NTRK testing guidelines were commonly reviewed by physicians (89%).Conclusion and RelevanceAmong patients with advanced/metastatic TRK fusion cancer, medical oncologists reported testing for NTRK fusions at diagnosis or prior to 1L. Future research should elucidate why fewer than half of oncologists surveyed (46%) would not use TRKis after NTRK+ status confirmation, assess clinical practices among NTRK+ patients, and characterize treatment patterns and clinical outcomes in real-world settings.

Changing Landscape of Systemic Therapy in Biliary Tract Cancer.

Simple SummaryCancers from the bile ducts and gall bladder are lethal. Cure by surgery is not possible in most of these tumors as they are often identified in later stages. Unlike other cancers, they have few chemotherapy treatment options. Multiple clinical trials in the past decade failed and could not replace the combination of two drugs, gemcitabine and cisplatin, as the preferred drug in new cases. Patients who fail to respond to this combination do not have reliable treatment options. The success of therapy directed at a specific genetic change (mutation) and activating the patient’s immune system (alone or in combination with chemotherapy) are encouraging. If we follow the current trials, the focus is on these newer treatments, with there being a high chance they may replace traditional chemotherapy in the future.Biliary tract cancers (BTC) are often diagnosed at advanced stages and have a grave outcome due to limited systemic options. Gemcitabine and cisplatin combination (GC) has been the first-line standard for more than a decade. Second-line chemotherapy (CT) options are limited. Targeted therapy or TT (fibroblast growth factor 2 inhibitors or FGFR2, isocitrate dehydrogenase 1 or IDH-1, and neurotrophic tyrosine receptor kinase or NTRK gene fusions inhibitors) have had reasonable success, but <5% of total BTC patients are eligible for them. The use of immune checkpoint inhibitors (ICI) such as pembrolizumab is restricted to microsatellite instability high (MSI-H) patients in the first line. The success of the TOPAZ-1 trial (GC plus durvalumab) is promising, with numerous trials underway that might soon bring targeted therapy (pemigatinib and infrigatinib) and ICI combinations (with CT or TT in microsatellite stable cancers) in the first line. Newer targets and newer agents for established targets are being investigated, and this may change the BTC management landscape in the coming years from traditional CT to individualized therapy (TT) or ICI-centered combinations. The latter group may occupy major space in BTC management due to the paucity of targetable mutations and a greater toxicity profile.

61P Updated efficacy and ctDNA analysis of patients with TRK fusion lung cancer treated with larotrectinib

Neurotrophic tyrosine receptor kinase (NTRK) gene fusions are oncogenic drivers. Larotrectinib, a highly selective, central nervous system-active tropomyosin receptor kinase (TRK) inhibitor, demonstrated a 75% objective response rate (ORR) in 206 patients (Hong et al. ASCO 2021). We report efficacy and safety with circulating tumour DNA (ctDNA) analysis for patients (pts) with TRK fusion lung cancer treated with larotrectinib.

110P Updated efficacy and safety of entrectinib in patients (pts) with NTRK fusion-positive (NTRK-fp) NSCLC

Neurotrophic receptor tyrosine kinase (NTRK) gene fusions are oncogenic drivers in many solid tumours, including NSCLC. Entrectinib (a CNS-active, potent TRK inhibitor) has shown efficacy in pts with NTRK-fp NSCLC from the STARTRK-2 (NCT02568267) and STARTRK-1 (NCT02097810) trials: objective response rate (ORR) was 69% (n=9/13; 31 Oct 2018 cutoff). We present an updated analysis in this cohort. Eligible pts with locally advanced/metastatic NTRK-fp tumours with/without baseline CNS metastases were enrolled. At Wk 4 and then every 8 wks, tumour response was assessed by blinded independent central review (BICR) per RECIST v1.1. Primary endpoints: ORR and duration of response (DoR). Secondary endpoints included progression-free survival (PFS), overall survival (OS), intracranial (IC) ORR and safety (31 Aug 2020 data cutoff). A total of 22 pts with NTRK-fp NSCLC (NTRK1, n=13; NTRK2, n=3; NTRK3, n=6) were included in the efficacy-evaluable population (enrolment cutoff: 31 July 2019). Median age was 60.5 years (range 22–88); 18 pts (81.8%) had adenocarcinoma; 9 pts (40.9%) had received ≥2 prior systemic therapies; 14 pts (63.6%) were current/former smokers; 13 pts (59.1%) had investigator-assessed baseline CNS metastases. Entrectinib showed efficacy in pts with NTRK-fp NSCLC, including those with baseline CNS metastases (Table). IC-ORR was 55.6% (n=5/9) in pts with BICR-assessed CNS metastases. In the NTRK-fp NSCLC safety-evaluable population (n=39 pts who received ≥1 entrectinib dose), most (64.1%) treatment-related adverse events (TRAEs) were grade 1–2 and manageable upon dose modifications. TRAEs leading to dose reduction, dose interruption and discontinuation occurred in 28.2%, 25.6% and 5.1% of pts, respectively. There were no grade 5 TRAEs. In this updated analysis with longer follow-up and more pts, entrectinib was associated with deep and durable responses in pts with NTRK-fp NSCLC, including those with baseline CNS metastases.Table: 110PAll pts (n=22)Pts with baseline CNS metastases* (n=13)Pts without baseline CNS metastases* (n=9)ORR, n (%) [95% CI]14 (63.6) [40.7–82.8]7 (53.8) [25.1–80.8]7 (77.8) [40.0–97.2]Complete response (CR)2 (9.1)1 (7.7)1 (11.1)Partial response12 (54.5)6 (46.2)6 (66.7)Stable disease3 (13.6)3 (23.1)0Progressive disease (PD)1 (4.5)1 (7.7)0Non CR/PD1 (4.5)01 (11.1)Missing/unevaluable3 (13.6)2 (15.4)1 (11.1)Median time to event, months (95% CI)DoR19.9 (10.4–29.4)†29.4 (13.0–NE)‡19.9 (9.2–NE)§PFS14.9 (6.5–30.4)13.8 (4.5–NE)17.8 (10.1–NE)OSNE (20.8–NE)NE (5.9–NE)NE (20.8–NE)*Investigator-assessed CNS metastases; †n=14; ‡n=7; §n=7. CI, confidence interval; NE, not estimable. Open table in a new tab

NTRK Fusion in Non-Small Cell Lung Cancer: Diagnosis, Therapy, and TRK Inhibitor Resistance.

Neurotrophic tropomyosin receptor kinase (NTRK) gene fusion has been identified as an oncogenic driver of various solid tumors, and it is rare in non-smalll cell lung cancer (NSCLC) with a frequency of approximately less than 1%. Next-generation sequencing (NGS) is of priority for detecting NTRK fusions, especially RNA-based NGS. Currently, the tropomyosin receptor kinase (TRK) inhibitors have shown promising efficacy and well tolerance in patients with NTRK fusion-positive solid tumors, regardless of tumor histology. The first-generation TRK inhibitors (larotrectinib and entrectinib) are recommended as the first-line treatment for locally advanced or metastatic NSCLC patients with positive NTRK fusion. However, TRK inhibitor resistance can eventually occur due to on-target or off-target mechanisms. Further studies are under investigation to overcome resistance and improve survival. Interestingly, NTRK fusion might be the mechanism of resistance to epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKI) in NSCLC patients with EGFR mutation. Regarding immunotherapy, the efficacy of immune checkpoint inhibitors in NSCLC patients harboring NTRK fusion has yet to be well described. In this review, we elucidate the function of NTRK genes, summarize the diagnostic techniques for NTRK fusions, and present clinical data for TRK inhibitors; we also discuss potential mechanisms of resistance to TRK inhibitors.

The Value of Online CME in the Multidisciplinary Care of Patients with NTRK Fusion-Positive Thyroid Cancer

<h3>Purpose/Objective(s)</h3> Neurotrophic tyrosine receptor kinase (<i>NTRK</i>) gene fusions are classified as actionable, but rare molecular markers in thyroid cancer (TC). Recently, two targeted therapies have been approved for pediatric and adult patients with advanced or metastatic solid tumors with <i>NTRK</i> gene fusions, marking the first small molecule inhibitor with a tissue agnostic indication. As a result of these advancements and the changing treatment landscape, staying current with emerging data and the impact on TC treatment paradigms can be challenging. The objective of this study was to determine if an online continuing medical education (CME) intervention could improve oncologists' and endocrinologists' understanding of <i>NTRK</i> gene fusions and available treatment options for patients with <i>NTRK</i> fusion-positive TC. <h3>Materials/Methods</h3> The activity consisted of a 40-minute video discussion between two expert faculty. Educational effect was assessed with a repeated pairs pre-/post-assessment study including a 3-item, multiple choice, knowledge questionnaire and one confidence assessment question, with each participant serving as his/her own control. Pre- and post-assessment scores were compared to determine relative changes in the proportion of correct responses to knowledge questions. A paired samples t-test assessed overall number correct and confidence change and a McNemar's test assessed individual question statistical significance. The activity launched 5 May 2021; data were collected until 30 July 2021. <h3>Results</h3> The total number of learners was 650 (oncologists, N=192; endocrinologists, N=458). Overall, statistically significant improvements in knowledge were seen after education consumption for responding oncologists (N=60, <i>P <</i> .01) and endocrinologists (N=101, <i>P</i> < .001). Relative improvement in correct answers was 35% for oncologists and 54% for endocrinologists (total correct responses pre-/post-assessment were 46%/62% and 35%/54%, respectively). When evaluating outcomes by individual knowledge learning objective, statistically significant improvements were observed for both oncologists and endocrinologists (<i>P</i> < .05). Following the activity, 43% of oncologists and 50% of endocrinologists had a measurable increase in confidence regarding their ability to coordinate the care of patients with <i>NTRK</i> fusion-positive TC with other members of the healthcare team. <h3>Conclusion</h3> Participation in an online, video discussion-based CME-certified activity resulted in statistically significant improvements in knowledge and measurable increases in confidence of oncologists and endocrinologists regarding <i>NTRK</i> gene fusions and available treatment options for patients with <i>NTRK</i> fusion-positive TC. The need for additional educational activities was also identified to address residual gaps and further increase clinicians' ability in this clinical setting.

44P A first-in-human, open-label, dose-escalation study to investigate the safety and tolerability of CHC2014, a tropomyosin receptor kinase (TRK) inhibitor, in adult patients with advanced solid tumors

TRK inhibitors are used to treat adult and pediatric patients with solid tumors based on the presence of a neurotrophic tyrosine receptor kinase (NTRK) gene fusion. CHC2014, a highly selective pan-TRK inhibitor, shows anti-tumor activity against tumors harboring wild-type or solvent front mutated NTRK fusions in non-clinical studies. This is the first-in-human dose-escalation study of oral pan-TRK inhibitor, CHC2014, in subjects with advanced solid tumors.

31P Molecular testing, treatment and outcome of patients with advanced solid tumors harboring a NTRK1, NTRK2 or NTRK3 gene fusion: Study design and first results of the REALTRK registry

Neurotrophic Tyrosine Receptor Kinase gene fusions involving either NTRK1, NTRK2 or NTRK3 (encoding the tropomyosin receptor kinases TRKA, TRKB and TRKC, respectively) are oncogenic drivers. The overall prevalence of NTRK fusion-positive tumors is ∼0.30%, though frequencies vary by tumor type, with >90% reported for rare tumor types such as secretory carcinoma of the breast and salivary glands. In Europe, two TRK inhibitors (entrectinib and larotrectinib) received tumor-agnostic approval. A very good clinical activity and a favorable overall safety profile was shown for both, making this new targeted approach highly relevant for patients with NTRK-fused tumors.