Phase II study of vismodegib in patients with SMO or PTCH1 mutated tumors: Results from NCI-MATCH ECOG-ACRIN Trial (EAY131) Subprotocol T.

3010 Background: NCI-MATCH (EAY131) is a platform trial enrolling patients (pts) with solid tumors, lymphomas, or multiple myeloma to targeted therapies based on matching genomic alterations (NCT02465060). Subprotocol Arm T evaluated vismodegib (GDC0449), a hedgehog signaling pathway inhibitor with anti-tumor activity in pts with tumors harboring PTCH1 and SMO mutations. Methods: Pts whose tumors had SMO or PTCH1 mutations were eligible; results were confirmed by NCI-MATCH central labs if possible. Pts received oral vismodegib (150 mg daily) for 4-week cycles until progression/toxicity. Tumor response was assessed every 2 cycles. Primary endpoint was ORR; secondary endpoints included PFS, 6-month PFS, OS, and predictive biomarkers. Cutaneous basal cell carcinomas were excluded. Results: Of 34 pts enrolled (6/20/16 – 9/22/20); 2 were ineligible and 1 did not start therapy. The 31 analyzable pts’ demographics were primary tumor sites/histology [gastrointestinal (n = 9), skin/soft tissue (n = 7), gynecologic (n = 5), lung (n = 4), unknown primary (n = 4), ductal breast (n = 1), meningioma (n = 1)]; median age 64 (range 19-81); 48.4% women; 61.3% (19/31) > 3 lines of prior therapy; 74% (23/31) > 1 co-occurring mutation [median 2 co-alterations (range 1-20)]. 8/31 > 4 co-occurring alterations. 9 pts had SMO mutant tumors (all SNVs); 5/9 had > 1 co-occurring gene alterations. 22 pts had PTCH1 alterations (7 SNVs and 15 indels); 18/22 pts had > 1 additional gene alteration. Of 31 analyzable pts, 22 were MATCH-confirmed (i.e. had central confirmation of tumor PTCH1/SMO mutations). MATCH-confirmed pts had ORR 9.1% (2/22) while all analyzable pts had ORR 6.5% (2/31). 2 PRs were seen in pts with a skin/soft tissue sarcoma ( PTCH) and a meningioma ( SMO) with a median duration of response 14 months. The 6-month PFS rate was similar in MATCH-confirmed and analyzable pts (22.4% and 23.2% respectively) and median PFS was identical at 1.8 months. Median OS was 9.1 months in MATCH-confirmed and 7.3 months in analyzable pts. Within analyzable SMO variants: 1 PR, 3 SD, 4 PD, and 1 unevaluable responses were documented. Within analyzable PTCH1 variants: 1 PR, 7 SD, 10 PD, and 4 unevaluable responses were seen. 4 pts (12.9%) discontinued therapy due to AE. Among 33 pts starting therapy, 18 (54.5%) had grade 1-2 toxicity, while 2 (6.1%) had grade 3 treatment-related toxicity. Most common toxicities: grade 1-2 fatigue (n = 11), anorexia (n = 8), weight loss (n = 7), alopecia (n = 7), and dysgeusia (n = 6). There were 4 on-study deaths, but none were treatment related. Conclusions: Although the primary endpoint was not reached, vismodegib was well-tolerated with mostly grade 1-2 toxicities and substantial responses were seen in patients with SMOPro641Ala and PTCHGlu947Ter alterations. Further study of the impact of concomitant molecular alterations may yield additional insights into vismodegib mechanisms of response. Clinical trial information: NCT02465060.