Subbiah, Vivek

Abstract Background: Activating receptor-tyrosine kinase rearranged during transfection (RET) mutations and fusions have been recognized as potent drivers of oncogenesis in multiple malignancies. Recently, highly potent and selective RET inhibitors, selpercatinib and pralsetinib have been FDA approved for RET fusion+ NSCLC and selpercatinib for RET+ thyroid cancers. Here we present a comprehensive analysis of RET alterations in pan-cancer adult malignancies. Patients and methods: 96,324 samples from 89,754 patients available from AACR Project Genie database version 8 were analyzed for the prevalence of RET fusions, mutations, and copy number alterations in diverse cancer types accessed July 21, 2020. The races of the samples within the cohort were 69,962 (72.6%) white, 5,388 (5.6%) Black, 4,909 (5.1%) Asian, 163 (0.17%) Native American, 48 (0.05%) Pacific Islander, and 15,854 (16.5%) were unknown. Results: There were 56,382 (58.5%) samples from primary tumors, 24,204 (25.1%) samples from unspecified metastasis sites, 4,798 (5.0%) from distant organ metastasis, 1,379 (1.4%) from lymph node metastasis, 1,279 (1.3%) from local recurrence, and 8,282 (8.6%) unknown. In 96,324 tumor samples there were 2,706 (2.81%) RET alterations. This included 223 (0.23%) fusions, 1,689 RET mutations found (1.75%) in 21 tumor histologies, and 794 (0.82%) RET amplifications identified; where the most abundant tissues harboring RET fusions were NSCLC (n = 121), papillary thyroid cancer (n = 53), breast cancer (n = 8) and colorectal cancer (n = 7) and the most abundant tissues harboring RET missense mutations were NSCLC (n = 355), colorectal cancer (n = 292), melanoma (n = 236), and thyroid cancer (n = 127). NSCLC samples with RET fusions had significantly co-altered KRAS, SETD2, PVRL4, EZH1, and RRAGC. Conclusions: RET fusions represent extremely rate events in multiple cancers. RET missense mutations occur in 2% of malignancies. Most RET missense variants are described as variants of unknown significance, limiting the impact of precision oncology for the majority of patients with RET alterations. Further functional characterization of RET variants is warranted because RET is highly targetable with therapeutics. Citation Format: Jacob J. Adashek, Alexander Andreev-Drakhlin, Jason Roszik, Aakash P. Desai, Vivek Subbiah. The landscape of 2,706 RET alterations from 89,754 adult patients with cancer: Clinical implications [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1221.

11523 Background: Sarcoma pts often receive aggressive, highly immunosuppressive therapy and may be at high risk for severe COVID-19. Demographics, outcomes and risk factors for pts with sarcoma and COVID-19 are unknown. We aimed to describe the course of COVID-19 in sarcoma pts and to identify factors associated with adverse outcomes. Methods: The COVID-19 and Cancer Consortium (NCT04354701) is an international registry of pts with cancer and COVID-19. Adult pts (≥18 years old) with a diagnosis of sarcoma and laboratory confirmed SARS-CoV-2 were included from 50 participating institutions. Data including demographics, sarcoma diagnosis and treatment, and course of COVID-19 infection were analyzed. Primary outcome was the composite rate of hospitalization or death at 30 days from COVID-19 diagnosis. Secondary outcomes were 30 day all-cause mortality, rate of hospitalization, O2 need, and ICU admission. Descriptive statistics and univariate Fisher tests are reported. Results: From March 17, 2020 to February 6, 2021, N=204 pts were included. Median follow up was 42 days. Median age was 58 years (IQR 43-67). 97 (48%) were male. 30 (15%) had ECOG performance status ≥2. 104 (51%) received cancer treatment, including surgery or radiation, within 3 months of COVID-19 diagnosis. 153 (75%) had active cancer, of whom 34 (22%) had lung metastases. 100 (49%) pts met the composite primary endpoint; 96 (47%) were hospitalized and 18 (9%) died within 30 days from COVID-19 diagnosis. 64 (31%) required oxygen, and 16 (8%) required ICU admission. Primary endpoint rates were similar for pts who received cytotoxic chemotherapy (38/58, 66%) or targeted therapy (16/28, 57%). Pts with higher rates of the primary endpoint included patients ≥60 years old (59% vs 40%, OR 2.04, 95% CI 1.12-3.74, p=0.016), pts with ECOG PS ≥2 vs 0-1 (90% vs 41%, OR 12.2, 95% CI 3.44-66.8, p<0.001), pts receiving any systemic therapy within 3 months of COVID-19 diagnosis (62% vs 39%, OR 2.65, 95% CI 1.43-4.97, p=0.001), and pts with lung metastases (68% vs 42%, OR 2.77, 95% CI 1.19-6.79, p=0.013). Primary endpoint rates were similar across sarcoma subtypes (Table). Conclusions: This is the largest cohort study of pts with sarcoma and COVID-19 to date. Sarcoma pts have high rates of complications from COVID-19. Older patients, those with poor performance status, those recently receiving systemic cancer therapy, and those with lung metastases appear to have worse outcomes.[Table: see text]

9089 Background: RET fusions are targetable oncogenic drivers in 1–2% of non-small cell lung cancer (NSCLC). ARROW (NCT03037385) supported the US FDA approval of pralsetinib, a highly potent oral selective RET inhibitor for RET-altered NSCLC and thyroid cancer. Here, we present updated results for a larger population of patients with RET fusion–positive NSCLC enrolled in ARROW. Methods: ARROW is a phase 1/2 open-label study conducted at 84 sites in 13 countries. Phase 2 expansion cohorts included patients with RET fusion–positive NSCLC. Initially, all treatment-naïve patients were not candidates for platinum-based therapy, a requirement removed by protocol amendment in July 2019. Primary objectives are overall response rate (ORR; blinded independent central review [BICR] per RECIST v1.1), assessed for patients with baseline measurable disease, and safety. Results: Updated analyses were completed as of Nov 6, 2020 (data cut-off), for patients who initiated pralsetinib 400 mg QD by May 22, 2020 (enrollment cut-off). Efficacy results, including analyses for treatment-naïve patients enrolled after eligibility criteria were revised to allow candidates for platinum-based therapy, are shown in the Table. Conclusions: Pralsetinib showed rapid, potent, and durable clinical activity in patients with RET fusion-positive NSCLC (regardless of prior therapies), including poor prognosis patients not eligible for platinum-based therapy. Overall, pralsetinib was well-tolerated. These data highlight the need for RET testing early in the course of disease to identify candidates who may benefit from treatment with pralsetinib. Clinical trial information: NCT03037385. [Table: see text]

TPS4165 Background: Oncogenic activation of FGFR2 via genomic rearrangement, gene amplification, or point mutation in advanced solid tumors provides the opportunity for rapid clinical development of highly selective FGFR2 inhibitors using a precision oncology approach to deliver clinical benefit to genomically-defined patient (pt) populations. Unfortunately, this opportunity remains largely unrealized as current, non-selective small molecule inhibitors (pan-FGFRi) suffer from off-isoform toxicity (FGFR1-hyperphosphatemia; FGFR4-diarrhea) and on-target acquired resistance leading to only modest efficacy primarily limited to FGFR2-fusion+ intrahepatic cholangiocarcinoma (ICC). RLY-4008 is a novel, oral FGFR2 inhibitor designed to overcome the limitations of pan-FGFRi by potently and selectively targeting primary oncogenic FGFR2 alterations and acquired resistance mutations. We initiated a first-in-human (FIH) precision oncology study of RLY-4008 in advanced solid tumor pts with FGFR2 alterations with primary objectives to define the maximum tolerated dose/recommended phase 2 dose (MTD/RP2D) and adverse event (AE) profile of RLY-4008 and key secondary objectives to assess FGFR2 genotype in blood and tumor tissue, pharmacokinetics (PK), and anti-tumor activity. Methods: This is a global, multi-center, FIH dose escalation/expansion study of RLY-4008 (NCT04526106) in adult pts who have unresectable or metastatic solid tumors with FGFR2 alteration per local assessment, ECOG performance status 0-2, measurable or evaluable disease per RECIST 1.1, and who are refractory, intolerant, or declined standard therapy including pan-FGFRi. FGFR2 alteration will be confirmed retrospectively by central laboratory assessment. For the dose escalation (Ñ50), RLY-4008 is administered QD/BID on a continuous schedule with 4-week cycles according to a Bayesian Optimal Interval design that allows accelerated dose titration, additional accrual to dose levels declared tolerable, and exploration of alternative schedules if warranted. The MTD is determined via logistic regression of the dose limiting toxicity rate across all dose levels and an RP2D less than the MTD may be considered based on observed AEs, PK, and anti-tumor activity. Following dose escalation, the dose expansion (Ñ75) will treat pts with RLY-4008 at the MTD/RP2D and includes 5 groups with any prior therapy (except group 2): 1. FGFR2 fusion+ ICC pts; 2. FGFR2 fusion+ ICC pts with no prior FGFRi; 3. FGFR2 fusion+ pts with other solid tumors; 4. FGFR2-mutation+ solid tumor pts and 5. FGFR2-amplified solid tumor pts. The primary endpoints are MTD/RP2D and AE profile; key secondary endpoints are FGFR2 genotype in blood and tumor tissue, PK parameters; overall response rate, and duration of response per RECIST 1.1. US enrollment began SEP2020 and Europe/Asia start-up is underway. Clinical trial information: NCT04526106.

3079 Background: RET fusions are targetable oncogenic drivers in multiple solid tumor types. ARROW study (NCT03037385) data supported the US FDA approval of pralsetinib, a once-daily (QD) oral highly potent and selective RET inhibitor, for RET-altered metastatic non-small cell lung cancer (NSCLC) and advanced/metastatic thyroid cancer. Here we provide an update on the clinical activity of pralsetinib in patients (pts) with advanced RET fusion-positive solid tumors other than NSCLC and thyroid cancer (“other” RET fusion–positive solid tumors). Methods: The global ongoing ARROW study (84 sites in 13 countries) includes phase 1 dose-escalation (30–600 mg [QD or twice daily]) and phase 2 expansion cohorts (400 mg QD) defined by tumor type and RET alteration status. Primary objectives are overall response rate (ORR; blinded independent central review per RECIST v1.1) and safety. Results: Updated analyses were completed as of Nov 6, 2020 (data cut-off) for 21 pts with other RET fusion–positive solid tumors enrolled by May 22, 2020 (enrollment cut-off) (lung other than NSCLC, n = 4; pancreatic, n = 3; colon, n = 3; cholangiocarcinoma, n = 3; unknown primary [UP], n = 2; other, n = 6). Overall, 11 (52%) pts received ≥2 prior lines of therapy for metastatic disease. The most common RET fusion partners were CCDC6 and KIF5B (24% each), NCOA4 (19%), other (10%), and unknown (24%). Two pts with colon cancer were excluded from efficacy analyses due to other driver mutations ( KRAS, PIK3CB). In 19 evaluable pts, ORR was 53% (95% CI, 29–76) with 2 (11%) complete responses (CR) and 8 (42%) partial responses (PR). Responses occurred across multiple tumor types including 3/3 pts with pancreatic cancer (including a CR ongoing at 20.8 months on treatment), 2/2 pts with UP, 2/3 pts with cholangiocarcinoma, and in pts with mesenchymal, salivary duct, and lung carcinoid tumors. Median duration of response was 19.0 months (95% CI, 5.5–not estimable). Clinical benefit rate (proportion with CR, PR, or stable disease persisting ≥16 weeks) was 68% (95% CI, 43–87). Tumor shrinkage was observed in 89% of 18 evaluable pts with post-baseline tumor assessment. In all pts enrolled in ARROW who received pralsetinib 400 mg QD irrespective of tumor type (n = 471) the most common (≥25%) treatment-related adverse events (TRAEs) were increased aspartate aminotransferase (39%), anemia (35%), increased alanine aminotransferase (28%), constipation (26%), and hypertension (25%). Overall, 6% of pts discontinued treatment due to TRAEs. Conclusions: Pralsetinib showed robust, durable antitumor activity in patients with multiple RET fusion‒positive, heavily pre-treated, advanced solid tumors, and was well tolerated. These data highlight the need for broad RET testing to identify candidates who could benefit from treatment with pralsetinib. Enrollment of patients with other RET fusion–positive solid tumors in ARROW is ongoing. Clinical trial information: NCT03037385.

467 Background: Recent tumor-agnostic drug approvals have resulted in a paradigm shift in cancer treatment away from organ/histology specific indications to biomarker-guided tumor-agnostic approaches. Pralsetinib is a potent and selective RET inhibitor, which has recently been approved by the U.S. Food and Drug Administration (FDA) for the treatment of adults with metastatic RET fusion–positive non-small cell lung cancer (NSCLC) and is under New Drug Application review for RET mutant thyroid cancers by the FDA. RET fusions occur in up to approximately 7‒8% of patients with gastrointestinal malignancies, including pancreatic, liver, and colorectal cancers. There are currently no approved selective RET inhibitors for patients with RET fusion–positive solid tumors other than NSCLC and thyroid cancer. Here, we present data on the clinical activity of pralsetinib in patients with RET fusion–positive solid tumor types other than NSCLC enrolled in the Phase I/II ARROW study (NCT03037385). Methods: ARROW consists of a phase I dose escalation (30–600 mg once [QD] or twice daily) followed by a phase II expansion (400 mg QD) in patients with advanced RET-altered solid tumors. Primary objectives are overall response rate (ORR), per RECICT v1.1 and safety. Results: A total of 13 patients with RET fusion–positive thyroid cancer (12 papillary, 1 poorly differentiated; enrollment cutoff July 11, 2019) and 14 patients with RET fusion–positive solid tumors other than NSCLC and thyroid (3 pancreatic, 3 colon, 2 cholangiocarcinoma, 6 other; enrollment cutoff November 19, 2019) were enrolled in ARROW and received pralsetinib. At the February 13, 2020, data cutoff, the ORR (blinded central review) in response-evaluable patients with RET fusion–positive thyroid cancer was 91% (10/11; 95% CI: 59‒100) and disease control rate was 100% (95% CI: 72‒100). Treatment was ongoing in 7 of 11 patients. In RET fusion–positive solid tumors other than NSCLC and thyroid, ORR (investigator’s assessment) was 50% (6/12; 95% CI: 21‒79) and responses were observed in all patients with pancreatic cancer (3/3) and cholangiocarcinoma (2/2). Treatment was ongoing in 6 of 12 patients, including 2 of 3 patients with pancreatic cancer and 1 of 2 patients with cholangiocarcinoma. Responses were observed across multiple fusion genotypes. In the 27 patients with RET fusion–positive tumors other than NSCLC, most frequent treatment-related adverse events (TRAEs) were grade 1–2, and included anemia (33%), increased aspartate aminotransferase (33%), decreased white blood cell count (33%), hypertension (30%), increased alanine aminotransferase (26%), hyperphosphatemia (19%), and neutropenia (19%). No patients discontinued due to TRAEs. Conclusions: Pralsetinib demonstrated broad and durable antitumor activity across multiple advanced solid tumor types, regardless of RET fusion genotype, and was well tolerated. The study is ongoing. Clinical trial information: NCT03037385.

109 Background: RET gene fusions are targetable oncogenic drivers in multiple tumor types, including up to 20% of papillary thyroid cancers (PTC). Pralsetinib is an investigational, highly potent, selective inhibitor of oncogenic RET alterations. In the registration-enabling Phase 1/2 ARROW study (NCT03037385), pralsetinib demonstrated an overall response rate (ORR; response-evaluable patients [REP], central review) of 73% (19/26) in treatment-naïve patients and 61% (49/80; 2 pending confirmation) in platinum-exposed patients with RET fusion+ non-small cell lung cancer (NSCLC) and was well tolerated (data cut-off November 18, 2019). We provide an update on the clinical activity of pralsetinib in other RET fusion+ solid tumor types. Methods: ARROW consists of a phase 1 dose escalation (30–600 mg once [QD] or twice daily) followed by a phase 2 expansion (400 mg QD) in patients with advanced RET-altered solid tumors. Primary objectives were ORR and safety. Results: As of November 18, 2019, 29 patients with metastatic solid tumor types other than NSCLC (16 PTC, 1 undifferentiated thyroid, 3 pancreatic, 3 colon, 6 other) bearing a RET fusion have received pralsetinib. Efficacy data are presented for REP enrolled by July 11, 2019. In patients with thyroid cancer that is RET fusion+, ORR (investigator assessment) was 75% (9/12; all confirmed). Median (range) duration of response (DOR) was 14.5 (3.7+, 16.8) months (mo), with 67% of responding patients continuing treatment. Two patients with stable disease were continuing treatment at 11.5+ and 19.3+ mo. In other RET fusion+ cancers, ORR was 60% (3/5; all confirmed) with partial responses in 2/2 patients with pancreatic cancer (DOR 5.5, 7.4+ mo) and 1 patient with intrahepatic bile duct carcinoma (DOR 7.5 mo). Two patients with colon cancer had stable disease for 7.3 and 9.3 mo. Responses were observed across multiple fusion genotypes. In the entire safety population (all patients treated with 400 mg QD pralsetinib, regardless of diagnosis; n = 354), most treatment-related adverse events (TRAEs) were grade 1-2, and included increased aspartate aminotransferase (31%), anemia (22%), increased alanine aminotransferase (21%), constipation (21%) and hypertension (20%). Only 4% of patients in the safety population discontinued due to TRAEs. Conclusions: Pralsetinib demonstrated broad and durable antitumor activity across multiple advanced solid tumor types, regardless of RET fusion genotype, and was well tolerated. The study is ongoing and still enrolling patients in this cohort. Clinical trial information: NCT03037385.