Phase Ib study of talimogene laherparepvec (T-VEC) injection into liver metastases (LMs) in combination with intravenous (IV) atezolizumab in patients (pts) with metastatic triple-negative breast cancer (TNBC) or colorectal cancer (CRC).

Abstract

TPS725 Background: T-VEC is a genetically modified, oncolytic herpes simplex virus type 1 designed to selectively replicate within tumors and produce GM-CSF to enhance systemic antitumor immune responses. Atezolizumab is a monoclonal antibody checkpoint inhibitor (CPI) that targets PD-L1. The safety of intrahepatic administration of T-VEC has been demonstrated in a prior clinical trial (NCT02509507). A previous trial of T-VEC in combination with a CPI in advanced melanoma demonstrated improved responses compared to those with a CPI alone (Puzanov et al. JCO. 2016; 34:2619-26). We hypothesize that T-VEC combined with a CPI may also be effective in other tumor types. This phase 1b, multicenter study evaluates the safety of intrahepatic injection of T-VEC in combination with IV atezolizumab in pts with TNBC or CRC with LMs. Methods: The study will enroll up to 36 pts in two parallel cohorts (18 TNBC, 18 CRC) at sites in the USA, Europe, and Australia. The primary objective is to evaluate the incidence of dose-limiting toxicities (DLTs). Secondary objectives include objective response rate, lesion-level responses in injected and uninjected tumors, progression-free survival, and overall survival. Key eligibility criteria include age ≥ 18 years, confirmed diagnosis of TNBC or CRC with LMs, ECOG performance status 0/1, adequate organ function, disease progression during or after ≥ 1 prior standard-of-care systemic therapy for metastatic disease, and ≥ 1 measurable, injectable LM. T-VEC will be given by image-guided intralesional injection of up to 4 mL of 106 plaque forming units (PFU)/mL on day 1 and up to 4 mL of 108 PFU/mL every 21 days thereafter; atezolizumab 1,200 mg IV will be given on day 1 and every 21 days thereafter. The DLT-evaluation period is the first two cycles (1 cycle = 21 days). Interim safety analysis will occur after the first 4–6 pts have become DLT evaluable. Up to six cycles of T-VEC will be given with an additional 6 cycles allowed. After cycle three, nonhepatic lesions may be injected, subject to protocol-defined criteria. The study opened for enrollment in January 2018. (NCT03256344) Clinical trial information: NCT03256344.