Abstract CT014: Efficacy of intratumoral BO-112 with systemic pembrolizumab in patients with advanced melanoma refractory to anti-PD-1-based therapy: Final results of SPOTLIGHT203 phase 2 study

Abstract Background: BO-112 is a double stranded synthetic RNA formulated with polyethyleneimine that mimics a viral infection. Through dendritic cells activation, increase in CD8 T-cell infiltration and interferons induction, it produces an immunogenic cell death. Phase 1 study (NCT02828098) showed ORR 20% in patients (pts) with anti PD-1 resistant melanoma (mel). Hence phase 2 trial was designed. Study design: Single arm study (NCT04570332) with intratumoral BO-112 plus intravenous pembrolizumab in pts with mel (cutaneous, acral or mucosal) and confirmed progressive disease (PD) while on anti-PD1 based therapy. Pts were treated with BO-112, 1-2 mg on a weekly basis for 7 weeks and thereafter Q3W in 1-8 different lesions. Pembrolizumab 200 mg was administered Q3W. Primary endpoint was overall response rate (ORR) by RECIST 1.1 by independent reviewer. Secondary endpoints included disease control rate (DCR), progression free survival (PFS) and safety. Exploratory objectives included radiomic signatures, itRECIST and evaluation of tumor microenvironment. At least 20% of pts had to achieve response in order to consider primary endpoint met. Results: Recruitment was completed 24th August 2021 with 42 pts; female 43%; median age 66 (rank 27-88). Table summarizes basal characteristics. With 40 evaluable for response pts, 10 achieved response (25%): 3 complete response (CR) and 7 partial response (PR). 17 pts (44%) achieved a stable disease (SD), meaning a DCR of 68% with 18 pts still on treatment. The 4 pts with a baseline LDH>3xULN developed PD no later than week 8. Responses per histology were: 66% mucosal, 28% cutaneous, 0% acral. Responses per BRAF/NRAS status were: BRAF mutant (Mut) 43%, NRAS Mut 31%, and BRAF/NRAS wild type (WT) 17%. 33 pts (79%) had at least one BO-112 related adverse event (AE) being only in 2 cases grade>3 (G4 infusion reaction and G3 myalgia). Most common related AEs were asthenia, pyrexia, diarrhea, vomiting and chills. Study treatment was not discontinued in any pts due to related AE. Conclusions: The primary efficacy endpoint has been met. Additionally, disease control (PR+CR+SD) is meaningful and durable in a population with no current standard treatment options. Very high LDH levels (LDH >3xULN) and acral mel could predict poor outcome. Safety profile was manageable without treatment discontinuation due to AEs. N (ITT pts, 42) (%) AJCC8 M1C/D 19 (45) BRAF Mut 7 (17) WT 35 (83) Previous treatment Ipilimumab-nivolumab 6 (15) Anti PD-1 monotherapy 33 (79) Other combo 3 (7) Prior line indication Adjuvant 11 (26) Advanced 31 (74) LDH >ULN 17 (41) Best ORR (IRCR evaluable pts, N=40) Global Mucosal Cutaneous Acral ORR 10 (25) 2 (66) 8 (28) 0 PR 7 (18) 1 (33) 6 (21) 0 CR 3 (8) 1 (33) 2* (7) 0 SD 17 (43) 1 (33) 13 (45) 3 (37) PD 13 (33) 0 8 (28) 5 (63) *2 pts had pathologic CR and RECIST SD Citation Format: Iván Márquez-Rodas, Caroline Dutriaux, Philippe Saiag, Luis de la Cruz Merino, Eduardo Castanon Álvarez, Caroline Robert, Juan F. Rodríguez-Moreno, Ana M. Arance, Pablo Cerezuela-Fuentes, Henry Montaudié, Miguel F. Sanmamed, María González Cao, Julie Charles, María Pilar López Criado, Alfonso Berrocal, Enrique de Miguel, Elisa Funk-Brentano, Sorilla Prey, María del Carmen Álamo de la Gala, Javier Sánchez López, Helena Escuin-Ordinas, Sonia Macia, Marisol Quintero, Marya F. Chaney, Stéphane Dalle. Efficacy of intratumoral BO-112 with systemic pembrolizumab in patients with advanced melanoma refractory to anti-PD-1-based therapy: Final results of SPOTLIGHT203 phase 2 study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT014.