Abstract CT038: Comprehensive molecular characterization of clinical response to durvalumab plus pazopanib combination in patients with advanced soft tissue sarcomas: A phase 2 clinical trial

We aimed to determine the activity of the anti-VEGF receptor tyrosine-kinase inhibitor, pazopanib, combined with the anti-PD-L1 inhibitor, durvalumab, in soft tissue sarcoma (STS). Further, we performed molecular characterisation with whole exome and transcriptomic sequencing to identify the determinants of response. In this single-arm, phase 2 trial (NCT#03798106), we enrolled patients with metastatic and/or recurrent STS who had received up to two previous lines of systemic anticancer therapy and had at least one measurable lesion. Treatment consisted of pazopanib 800 mg orally, administered once a day, continuously, and durvalumab 1500 mg administered via intravenous infusion once every 3 weeks. The primary endpoint was the overall response rate. Between September 2019 and October 2020, fourteen (30.5%) of the 46 evaluable patients showed an objective response, including in alveolar soft-part sarcoma, angiosarcoma, undifferentiated pleomorphic sarcoma, and desmoplastic small round cell tumour. During a median follow-up period of 18.4 months, the median progression-free survival (PFS) was 7.7 months (95% confidence interval: 5.7-10.4). The common treatment-related adverse events of grades 3-4 included neutropenia (n = 9), elevated aspartate aminotransferase (n = 7) and alanine aminotransferase (n = 5) levels, and thrombocytopenia (n = 4). In the exploratory analysis, the B lineage signature was a significant key determinant of overall response (P=0.014). In situ analysis also showed that tumours with high CD20+ B cell infiltration and vessel density had a longer PFS than those with low B cell infiltration and vessel density (P=6.5 × 10−4) as well as better response (50% vs 12%, P=0.019). In conclusion, durvalumab combined with pazopanib demonstrated promising efficacy in an unselected STS cohort, with a manageable toxicity profile. Our findings provide insights into combined high B cell infiltration and vessel density as potentially relevant biomarkers for the selection of patients who may benefit to a greater extent from PD-L1 blockade and VEGF inhibitor combination. Citation Format: Hee Jin Cho, Kum-Hee Yun, Su-Jin Shin, Young Han Lee, Seung Hyun Kim, Wooyeol Baek, Yoon Dae Han, Sang Kyum Kim, JooHee Lee, Iksung Cho, Heounjeong Go, Jiwon Ko, Inkyung Jung, Min Kyung Jeon, Hyang Joo Ryu, Sun Young Rha, Hyo Song Kim, Hyun Jung Jun. Comprehensive molecular characterization of clinical response to durvalumab plus pazopanib combination in patients with advan