Durable responses to treatment with atezolizumab in advanced alveolar soft part sarcoma were seen across a phase 2 study.
The objective response rate (ORR) of patients who received atezolizumab for advanced alveolar soft part sarcoma (ASPS) was 42% and there were confirmed partial responses from 8 of 19 patients who were under investigation following treatment, reported Geraldine O’Sullivan Coyne, MD, of the National Cancer Institute (NCI) in Bethesda, Maryland, during a paper presentation at the Connective Tissue Oncology Society (CTOS) 2018 Annual Meeting in Rome, Italy.1
Median time to first response was at 5 cycles (range, 4-19 cycles) and the median time on treatment was 11 cycles (range, 1-25 cycles).
And perhaps even more striking was that 1 teenage patient with ASPS had a marked response, said Dr Coyne. The drug was administered to the patient under an individual-patient investigational new drug application (IND) following the discovery that high PD-L1 expression was reported in 2 xenograft models of ASPS through NCI’s Pediatric Preclinical Testing Consortium, which Dr Coyne said suggested “the PD-1 pathway likely contributes to immunosuppression in ASPS.”
The rarity of the ASPS tumor subtype presented an enrollment problem, so Dr Coyne described engaging the NCI to extend the clinical trial network via NCI’s Experimental Therapeutics Clinical Trials Network, meant to promote collaboration among people working on the same research questions, conduct early clinical trials of NCI IND agents in cancers that have no or few treatment options, and “integrate preclinical findings using clinical samples for biomarker analysis,” Dr Coyne explained.
In the phase 2, Simon 2-stage design, the researchers wanted to see at least 3 responders out of the 24 evaluable patients to make the determination that the medication would be an “interesting regimen to pursue further.”
Patients who were eligible for enrollment in the trial were adult or pediatric patients aged 6 years and older who had a confirmed ASPS diagnosis, an Eastern Cooperative Oncology (ECOG) score of 2 or less, no measurable disease outside of the central nervous system, PD-1 and PD-L1 therapy-naive, no grade 3 or higher immune-related events from treatment with anti-CTLA4 therapies, and no history of autoimmune disease. At the date of the presentation, there were no pediatric patients enrolled in the trial, although Dr Coyne emphasized it would be permitted.
Enrollment for the trial will continue into a second stage, with new patient slots planned in biopsy and correlative analysis. And, additional cohorts are planned in clear cell sarcoma and chondrosarcoma.
For her contribution to the NCI study, Dr Coyne received a Young Investigator Award from the CTOS conference organizers during a special ceremony.
Read more of Cancer Therapy Advisor‘s coverage of the CTOS 2018 meeting by visiting the conference page.
- O’Sullivan Coyne G, Sharon E, Moore N, et al. Phase 2 study of atezolizumab in patients with alveolar soft part sarcoma. Presented at: CTOS 2018 Annual Meeting; Rome, Italy: November 14-17. Paper 021.