A phase 2 clinical trial of axitinib and avelumab in patients with recurrent/metastatic adenoid cystic carcinoma (ACC)

ABSTRACT

Background: ACC is a heterogeneous neoplasm and there is no standard treatment for patients (pts) with recurrent/metastatic (R/M) disease. Vascular endothelial growth factor receptor inhibitors (VEGFRi) are frequently used to treat R/M ACC rendering mostly disease stabilization. ACC is resistant to PD-1/PD-L1 inhibitors (PD-L1i), consistent with its low mutational burden and uninflamed immune microenvironment. We hypothesized that the immunomodulatory role of VEGFRi (axitinib) would enhance PD-L1i (Avelumab) activity and be a more effective therapy for R/M ACC. Methods: Eligible pts had R/M ACC with radiological or clinical progression within 6 months (mos) of enrollment. Treatment consisted of axitinib 5 mg PO bid and avelumab 10 mg/Kg IV every 2 weeks. Primary endpoint was objective response rate (ORR) per RECIST 1.1;secondary endpoints included duration of response (DOR), progression-free survival (PFS), overall survival (OS), and toxicity. Simon 2-stage design was applied to test the null hypothesis of ORR ≤ 5% versus the alternative ORR ≥ 20%;≥ 4 responses out of 29 pts was required to reject the null hypothesis. Results: 41 pts enrolled from 07/24/19 to 06/29/ 21;28 were evaluable for the primary endpoint (7 screen failures, 6 evaluable for safety only due to loss of insurance/logistics issues related to COVID-19 pandemic);16 pts were treated in first-line. Mutation data was available for 23 of 28 evaluable pts;7 had NOTCH1 activating mutations. The ORR was 17.9% (5/28, 95%CI 6.1-36.9%). One response was unconfirmed (pt progressed in non-target lesions 2 mos after achieving a PR), for a confirmed ORR of 14.3% (95%CI 4-32.7%). The median follow-up time for the 15 alive pts was 11.6 mos (min-max 7.7-29.2 mos). Median PFS was 7.2 mos (95%CI 3.7-11.7 mos) with a 6-mos PFS rate of 57% (95%CI 41-79%). Median OS was 17.4 mos (95%CI 13-NA). 5 pts remain on therapy, 2/5 with a PR. The median DOR for the 5 responders was 5.2 mos (95% CI 3.7-NA mos). The most common treatment-related adverse events (TRAEs) were fatigue (62%), hypertension (32%), diarrhea (29%), and stomatitis (29%). Serious TRAEs occurred in 8 (24%) pts, all grade 3 and manageable. 4 (15%) pts discontinued avelumab and 9 (32%) underwent axitinib dose reduction due to toxicity. Conclusions: The study reached its primary endpoint with ≥ 4 responses out of 28 evaluable pts (ORR of 17.8%;confirmed ORR of 14.3%). The ORR and 6- mos PFS rate of 57% with axitinib and avelumab compares favorably with single agent axitinib and warrants further study of the combination.