Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

BACKGROUND: We evaluated MK-4621, an oligonucleotide that binds and activates retinoic acid-inducible gene I (RIG-I), as monotherapy (NCT03065023) and in combination with the anti-programmed death 1 antibody pembrolizumab (NCT03739138). PATIENTS AND METHODS: Patients were ≥ 18 years with histologically/cytologically confirmed advanced/metastatic solid tumors with injectable lesions. MK-4621 (0.2‒0.8 mg) was administered intratumorally as a stable formulation with jetPEI™ twice weekly over a 4-week cycle as monotherapy and weekly in 3-week cycles for up to 6 cycles in combination with 200 mg pembrolizumab every 3 weeks for up to 35 cycles. Primary endpoints were dose-limiting toxicities (DLTs), treatment-related adverse events (AEs), and treatment discontinuation due to AEs. RESULTS: Fifteen patients received MK-4621 monotherapy and 30 received MK-4621 plus pembrolizumab. The only DLT, grade 3 pleural effusion that subsequently resolved, occurred in a patient who received MK-4621/jetPEI™ 0.8 mg plus pembrolizumab. 93% of patients experienced ≥ 1 treatment-related AE with both monotherapy and combination therapy. No patients experienced an objective response per RECIST v1.1 with MK-4621 monotherapy; 4 (27%) had stable disease. Three (10%) patients who received combination therapy had a partial response. Serum and tumor biomarker analyses provided evidence that MK-4621 treatment induced an increase in gene expression of interferon signaling pathway members and associated chemokines and cytokines. CONCLUSIONS: Patients treated with MK-4621 monotherapy or in combination with pembrolizumab experienced tolerable safety and modest antitumor activity, and there was evidence that MK-4621 activated the RIG-I pathway. At the doses tested, MK-4621 did not confer meaningful clinical benefit. TRIAL REGISTRATION:, NCT03065023 and NCT03739138.

Original publication




Journal article


Cancer Immunol Immunother

Publication Date





2985 - 2998


Innate immunity, Interferon type I, Intratumoral injection, Pembrolizumab, RIG-I, Humans, Neoplasms, Biomarkers, Tumor, Interferons, Cytokines, Oligonucleotides, Tretinoin, Antineoplastic Combined Chemotherapy Protocols