Phase II randomized window of opportunity trial evaluating cytotoxic and immunomodulatory effects of intratumoral INT230-6 in early stage breast cancer: The INVINCIBLE trial.

573 Background: Most breast cancers are considered immunological cold and are therefore minimally responsive to immunotherapies. Local cytotoxic therapies can induce cell death, expose tumor antigens, provide adjuvants for anti-tumor immune priming, and potentially increase responsiveness to immunotherapies. We conducted a randomized, double blind, Phase 2 presurgical Window-Of-Opportunity trial for intratumoral (IT) INT230-6 (comprising VINblastine (VIN) Cisplatin (VIN)) evaluating clinical and BioLogical Effects in patients with early-stage operable Breast Cancer (the INVINCIBLE trialNCT04781725. The trial evaluated the immune response within the tumor and microenvironment in vivo after IT INT230-6 injections. Methods: Women with newly diagnosed and awaiting surgery for early-stage intermediate or high-grade ER+ T1-T2 invasive breast cancers were recruited to the trial. Participating patients were allocated (2:1) to IT injections of INT230-6 vs saline placebo, prior to resection. RNA profiling of the pre- (baseline biopsy) and post- treatment (surgical resection) tumours using the Ion AmpliSeq Transcriptome Human Gene Expression (Thermo Fisher Scientific) and DNA sequencing using a large (500 gene) comprehensive genomic profiling panel (OCAPlus,) was performed. Results: Significant tumor necrosis was observed in the majority of subjects injected with INT230-6. In the 60 pre-treatment biopsies profiled with OCAPlus, the genes most frequently mutated included PIK3CA (38%), TP53 (23%), CDH1 (22%) and TBX3 (17%). Frequent copy number changes were identified in CCND1 (23%), FGFR1 (18%), and CDH1 (17%). Gene expression analysis showed significant differential gene expression between the baseline biopsy and surgical specimens in patients treated with the drug. Pathway analysis identified genes associated with TCR signaling, macrophage markers, IL-18 signaling and B cell receptor signaling were significantly up-regulated in the post treatment samples. Conclusions: This is the first study evaluating the potential biologic effects of intratumoral cytotoxicity with INT230-6 and its role as a potential immune priming therapy in traditional immune quiescent ER+ breast cancers.