Abstract B23: A pilot study targeting angiogenesis using bevacizumab combined with gemcitabine/docetaxel and valproic acid (VPA), a histone deacetylase inhibitor (HDACi), in advanced soft tissue sarcomas (STS)

Introduction: Many of the signaling pathways involved in angiogenesis also drive STS tumor cell growth. Autocrine and paracrine vascular endothelial growth factor (VEGF) and platelet-derived growth factor mediated growth plays a role in the pathogenesis of several STS subtypes. Relatively few clinical trials have evaluated the role of combining angiogenesis inhibitors, like bevacizumab, with chemotherapy in sarcoma with mostly negative results. We hypothesized that the microenvironment may prevent bevacizumab from truly blocking angiogenesis and that there may exist an “angiogenic switch” that is epigenetically mediated. Epigenetically modifying the tumor microenvironment prior to chemotherapy has been shown to improve cytotoxic cell kill and response rates. Gain-of-function p53 mutant tumors are poor chemotherapy responders and cause genome-wide increase in histone methylation and acetylation. VPA is a known HDACi with antitumor effects and suppresses neovascularization. Herein we combined pulse dose of VPA with bevacizumab and standard chemotherapy (gemcitabine/docetaxel) to better modulate the cytotoxic effects against STS. Materials and Methods: Subjects with locally advanced, unresectable, or metastatic STS of any site and all subtypes with measurable disease were enrolled. GIST, bone, and Kaposi9s sarcomas were excluded. VPA at 40-mg/kg dosage was given for 5 days prior to each cycle and was repeated before each cycle. Gemcitabine 900 mg/m2 on days 1 and 8 and docetaxel 75 mg/m2 on day 8 were administered on a 28-day schedule. Bevacizumab 15 mg/kg every 4 weeks was administered on day 1 throughout chemotherapy and after chemotherapy was completed. Subjects were treated for a total of 6 cycles and assessed every 2 cycles for progression. Treatment was terminated on disease progression or with unacceptable toxicity. All pathologic diagnoses were confirmed by a pathologist with subspecialty training in bone and soft-tissue pathology. Results: 46 subjects (30 female, 16 male) with median age of 60 (range 24-81) years and a median of 1 (range 0-6) prior line of chemotherapy were enrolled. Sarcoma subtypes included extrauterine leiomyosarcoma (LMS) (9), uterine LMS (8), undifferentiated pleomorphic (7), angiosarcoma, carcinosarcoma, liposarcoma (4 each), and other types (10). 34 (73.9%) subjects received prior chemotherapy, 14 (30%) of whom received prior gemcitabine and docetaxel. 16 (34.8%) received prior radiation and 44 (95.7%) had prior surgery. 5 (12%) of 41 subjects had gain-of-function p53 mutation. Subjects received a median of 5.5 cycles (0-15) of treatment. 17 subjects underwent dose reduction of which VPA was reduced in 6 subjects. 42 subjects were evaluable for response. There was a complete response in 1 (epithelioid) and a partial response (PR) in 6 (1 carcinosarcoma, 2 extrauterine LMS, 2 undifferentiated pleomorphic, and 1 uterine LMS) subjects. Stable disease (SD) was seen in 21 subjects. One subject with prior gemcitabine and docetaxel had PR and 7 had SD. Median progression-free survival (PFS) was 5.7 months (95% CI: 2.1-8) and overall survival (OS) was 12.9 months (95% CI: 8.3-14.5). In LMS subgroup median PFS was 8.4 months (95% CI: 2-8.6) and median OS was 16.3 months (95% CI: 8.1-26.5). Grade 3/4 bevacizumab and VPA-related hematologic toxicities were observed in 2% and 13% and nonhematological toxicities in 9% and 13% of subjects, respectively. Conclusions: Addition of VPA and bevacizumab to gemcitabine and docetaxel showed a clinical benefit rate of 61.54 % in subjects with prior gemcitabine and docetaxel. This regimen is safe and toxicities are manageable. The overall response rate in the study was 16.67%. The combination deserves further investigation in epithelioid and carcinosarcoma subgroups. Citation Format: Umang Swami, Varun Monga, Munir Tanas, Aaron Bossler, Sarah Mott, Brian Smith, Mohammed Milhem. A pilot study targeting angiogenesis using bevacizumab combined with gemcitabine/docetaxel and valproic acid (VPA), a histone deacetylase inhibitor (HDACi), in advanced soft tissue sarcomas (STS) [abstract]. In: Proceedings of the AACR Conference on Advances in Sarcomas: From Basic Science to Clinical Translation; May 16-19, 2017; Philadelphia, PA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(2_Suppl):Abstract nr B23.