Abstract CT032: Activity and safety of alectinib for ALK-altered solid tumors from MyPathway

Abstract Purpose: Alectinib is FDA-approved for ALK-positive, metastatic non-small cell lung cancer (NSCLC). We analyzed alectinib treatment in a pan-tumor population with ALK alterations from MyPathway (NCT02091141), a multi-basket study assessing approved therapies in non-indicated advanced solid tumors with relevant alterations. Methods: Enrolled patients (pts) were ≥18 yrs old and had metastatic tumors with ALK gene rearrangements, putative activating non-synonymous ALK mutations, and/or ALK gene amplification. Pts received alectinib 600 mg PO BID. The primary endpoint was investigator-assessed objective response rate (ORR; complete response [CR] + partial response [PR]). Other endpoints included duration of response (DOR), disease control rate (DCR; CR + PR + stable disease [SD] >4 mos), progression-free survival (PFS), and safety. Results: By the 11-18-2021 data cutoff, 21 pts with various tumor types had been enrolled and treated (ALK mutations or amplification, n=11 [52.4%]; ALK rearrangements +/- other ALK alterations, n=10 [47.6%]). Pts had a median of 2 (range, 1-5) prior lines of therapy. In the 10 pts with ALK rearrangements, there were 3 PRs (30.0%) with a median DOR of 6.8 mos (Table). An additional 3 pts in this group had SD >4 mos; DCR was 60.0% (6/10). In contrast, there were no responses among the 11 pts with ALK mutations or amplification. Confirmed ORR for the entire group was 14.3% (3/21), and DCR was 42.9% (9/21). Median PFS was 8.2 mos in pts with ALK rearrangements vs 1.8 mos for those with other ALK alterations. Alectinib-related adverse events (AEs) were observed in 85.7% of pts, with 3 (14.3%) experiencing grade 3 AEs (anemia; hypokalemia; and changes in AST, ALT, and/or blood creatinine levels). AEs were consistent with the known alectinib safety profile. Conclusions: Although the number of pts is small, alectinib appears active in those with non-NSCLC advanced solid tumors with ALK rearrangements. As in NSCLC, cancers with ALK mutations or amplification were not responsive to ALK inhibition. Table. Clinical outcomes Clinical Response Rearrangement (n=10) Mutation (n=7) Amplification (n=4) Median PFS, mos (all alterations) n Indications n Indications n Indications PR 3a Melanoma, Papillary urothelial carcinoma, Colon adenocarcinoma 0 NA 0 NA 9.3 SD >4 mos 3b,c Colon adenocarcinoma, Uterine leiomyosarcoma, Pancreatic adenocarcinoma 2 Squamous cell carcinoma, Soft tissue sarcoma 1 Uterine body clear cell carcinoma 5.7 SD ≤4 mos 0 NA 1 Fallopian tube serous carcinoma 0 NA PD 3d,e Colon adenocarcinoma, Esophageal adenocarcinoma, Uterine serous carcinoma 4 Anaplastic thyroid carcinoma, Esophageal adenocarcinoma, Colon adenocarcinoma (2) 3 Ovarian serous carcinoma, Gastric squamous cell carcinoma, Peritoneal non-small cell carcinoma 1.7 Non-evaluable 1f Uterine inflammatory myofibroblastic tumor 0 NA 0 NA NA aFusion gene partners: EMILIN1, DCTN1, and DIAPH2. bOne pt with ALK rearrangement and SD >4 mos also had ALK amplification. cFusion gene partners: STRN, IGFBP5, and EML4. dPts with ALK rearrangement and PD also had an ALK mutation (n=1) or ALK amplification (n=1). eFusion gene partner: STRN; fusion genes unknown for 2 pts. fPt withdrew prior to clinical assessment and was censored for PFS at 0.03 mos. NA, not applicable; PD, progressive disease; PFS, progression-free survival; PR, partial response; SD, stable disease. Citation Format: Charles Swanton, Claire F. Friedman, Christopher J. Sweeney, Funda Meric-Bernstam, David Spigel, Ron Bose, Howard Burris, Walter C. Darbonne, Julia Malato, Jonathan Levy, Yong Wang, Tania Szado, Katja Schulze, John Hainsworth, Razelle Kurzrock. Activity and safety of alectinib for ALK-altered solid tumors from MyPathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT032.