Bowles, Daniel W.

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]

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.

6512 Background: Lenvatinib is an approved therapy for patients with RAIR DTC. While the overall response rate (ORR) is high, few patients achieve a complete response (CR) and most patients eventually have progressive disease (PD). Combination lenvatinib and pembrolizumab is being explored in many different cancers, and this combination has been approved for advanced endometrial carcinoma. Methods: Patients with RAIR DTC with Response Evaluation Criteria in Solid Tumor (RECIST v1.1) measurable PD (<14 months (mo) prior to registration) were enrolled in this single-arm multicenter phase II study. Patients were excluded if they had received previous VEGFR-directed multikinase therapy. The lenvatinib starting dose was 20 mg/day orally and pembrolizumab was 200mg IV every 3 weeks. The primary endpoint was CR. ORR, progression-free survival (PFS) and safety graded by Common Terminology Criteria for Adverse Events v4.0 were secondary endpoints. Results: Thirty patients were enrolled. The median age was 62.5 years, and 53% of the patients were women. Seventy percent of patients had grade 3 adverse events (AEs) and 10 percent had grade 4 AEs. There were no treatment-related deaths. The most common > grade 3 AEs were hypertension (47%), weight loss (13%), maculopapular rash (13%), leukopenia (7%), diarrhea (7%) and oral mucositis (7%). Twenty-one patients (70%) required lenvatinib dose reduction. Of 29 evaluable patients, 18 (62%) had a partial response (PR) and 10 (35%) had stable disease (SD). The clinical benefit rate (ORR +SD) was 97%. Median time to tumor nadir was 7.4 mo (1.6-17.8 mo). Median PFS was not yet reached. The PFS at 12 months was 74%. Median time on therapy was 9.9 mo (3.2-18.9 mo). Fourteen patients are continuing therapy (7.6-18.9 mo). Six of these patients (43%) have not yet reached tumor size nadir. Three patients (10%) had > 80% target tumor shrinkage. Conclusions: Lenvatinib plus pembrolizumab is reasonably tolerated in patients with RAIR DTC. To date, there have been no documented complete responses. Combination lenvatinib plus pembrolizumab therapy has a high ORR in patients with RAIR DTC. Continuation of this study will help determine the depth and length of the responses. Clinical trial information: NCT02973997 .

6020 Background: A subset of salivary gland cancer (SGCs) express the androgen receptor (AR). This phase II trial evaluated the anti-androgen enzalumatide (Astellas) for patients with AR+ SGCs. Methods: Locally advanced/unresectable or metastatic AR+ SGCs were enrolled (AR status was centrally confirmed). Prior therapy with AR-targeted drugs was allowed. Enzalutamide 160 mg orally once daily was given (1 cycle= 28 days). The primary endpoint was confirmed response (RR) according to RECIST v1.1 within the first 8 cycles. Secondary endpoints were progression-free survival (PFS), overall survival (OS), and safety. A Simon-Optimal two-stage design was used to detect a 20% RR (vs. 5%) (alpha = 5%; beta = 90%). > 1 response(s) in the first 21 would trigger accrual to 41; > 4 responses would be considered promising. Results: 46 eligible patients (pts) were enrolled (40 M, 6 F; median age 65) in 22 months. In the first 21 pts, we initially had 2 confirmed PRs allowing for full study accrual, though one was later changed to stable disease. Among the 46 pts, 7 had PR as best response, though only 2 were confirmed within the first 8 cycles (4% (95% CI: 0.5-15%). Two other PRs did not count towards the primary endpoint due to 1) development beyond 8 cycles (cycles 12-18) and 2) a confirmatory scan completed <4 weeks apart. The other 3 pts with unconfirmed PR developed progression of disease (PD) after the first PR scan. 24 pts had stable disease; 15 pts PD as best response. Among 11 pts previously treated with AR-targeted therapy, best responses were 1 confirmed PR, 7 SD, 3 PD. With a median follow-up of 11.7 months (mo), OS at 12 mo was 66% (95% CI: 52-83%), PFS at 12 mo was 24% (95% CI: 14-42%), and median PFS was 5.5 mo (95% CI: 3.7-7.3). Conclusions: This is the first prospective trial evaluating an antiandrogen alone for AR+ SGCs. The failure to meet the protocol-defined measure of success was due in part to the lack of durability of initial responses. The clinical activity observed suggests the AR-dependence of AR+ SGCs, even among those previously treated with other hormonal therapies. Support: U10CA180821, U10CA180882; Astellas; https://acknowledgments.alliancefound.org. Clinical trial information: NCT02749903.

Abstract Purpose: This first-in-human study assessed safety, tolerability, pharmacokinetics, pharmacodynamics, and preliminary clinical activity of single and multiple doses of TAK-441, an investigational inhibitor of the Hedgehog signaling pathway. Experimental Design: Patients with advanced, solid tumors received daily oral TAK-441 (50–1,600 mg/day); daily dose was doubled in each subsequent cohort until the maximum tolerated/feasible dose (MTD/MFD) was reached. Blood was collected to evaluate TAK-441 plasma concentrations. Skin biopsies were obtained to evaluate suppression of the Hedgehog-regulated gene Gli1. Results: Thirty-four patients were enrolled (median age 59). The most common diagnoses were colorectal cancer (26%), basal cell carcinoma (BCC, 21%), and pancreatic cancer (9%). The MFD of 1,600 mg/day (based on tablet size and strength) was considered the MTD. Dose-limiting toxicities included muscle spasms and fatigue. Grade ≥3 treatment-emergent adverse events, regardless of causality, occurred in 15 patients (44%), of which hyponatremia (n = 4) and fatigue (n = 3) were most common. Oral absorption was fairly rapid; median Tmax was 2.0 to 4.0 hours after a single dose. Mean elimination half-life was 13.5 to 22.6 hours. Systemic exposure of TAK-441 based on the area under the plasma concentration–time curve was linear across the dose range. Gli1 expression in skin biopsies was strongly inhibited at all dose levels. Best response was partial response (1 patient with BCC) and stable disease (7 patients with various solid tumors). Conclusions: TAK-441 was generally well tolerated up to MFD of 1,600 mg/day, with preliminary antitumor activity. Further study of TAK-441 may be appropriate in populations selected for tumors with ligand-dependent or independent Hedgehog signaling. Clin Cancer Res; 21(5); 1002–9. ©2014 AACR.