Kreider, Brent

Abstract Purpose: Intratumoral injection of Clostridium novyi-nontoxic (C. novyi-NT), lacking alpha-toxin, germinates and subsequently replicates in the tumor hypoxic regions, causing cell lysis and inflammation. This phase Ib study investigated the safety and synergistic effects of pembrolizumab and C. novyi-NT in advanced solid tumors. Patients and Methods: Patients with injectable solid tumors received one intratumoral C. novyi-NT injection (day 8) across four dose cohorts (3 × 104 to 100 × 104 spores) with pembrolizumab (200 mg intravenously every 3 weeks, day 0–24 months). Sixteen patients were enrolled with a median age of 62.5 years, and the most common tumor types were breast cancer and melanoma. Results: The combination therapy demonstrated a manageable safety profile, with one grade 3 dose-limiting toxicity of abscess formation and the remainder of treatment-related adverse events in ≥10% of patients being grade 1 or 2 injection site reaction (25%), pyrexia (19%), pruritus (13%), leukopenia (13%), and anemia (13%). The maximum tolerated dose was determined to be pembrolizumab intravenously at 200 mg every 3 weeks and a single dose of 100 × 104C.novyi-NT spores intratumorally on day 8. The confirmed overall objective response rate of 25% was observed among four patients with nonkeratinizing undifferentiated nasopharyngeal squamous carcinoma, human papilloma virus–positive squamous cell carcinoma of the base of the tongue, vulvar melanoma, and chordoma. Among these patients, we obtained three partial responses and one complete response. The median duration of the response was 10.93 months, and stable disease was observed in 69% of patients. Conclusions: This study highlights the potential of the C. novyi-NT and pembrolizumab combination as a promising therapeutic strategy for treatment-refractory solid tumors.

Abstract Purpose: Intratumorally injected Clostridium novyi-NT (nontoxic; lacking the alpha toxin), an attenuated strain of C. novyi, replicates within hypoxic tumor regions resulting in tumor-confined cell lysis and inflammatory response in animals, which warrants clinical investigation. Patients and Methods: This first-in-human study (NCT01924689) enrolled patients with injectable, treatment-refractory solid tumors to receive a single intratumoral injection of C. novyi-NT across 6 dose cohorts (1 × 104 to 3 × 106 spores, 3+3 dose-escalation design) to determine dose-limiting toxicities (DLT), and the maximum tolerated dose. Results: Among 24 patients, a single intratumoral injection of C. novyi-NT led to bacterial spores germination and the resultant lysis of injected tumor masses in 10 patients (42%) across all doses. The cohort 5 dose (1 × 106 spores) was defined as the maximum tolerated dose; DLTs were grade 4 sepsis (n = 2) and grade 4 gas gangrene (n = 1), all occurring in three patients with injected tumors >8 cm. Other treatment-related grade ≥3 toxicities included pathologic fracture (n = 1), limb abscess (n = 1), soft-tissue infection (n = 1), respiratory insufficiency (n = 1), and rash (n = 1), which occurred across four patients. Of 22 evaluable patients, nine (41%) had a decrease in size of the injected tumor and 19 (86%) had stable disease as the best overall response in injected and noninjected lesions combined. C. novyi-NT injection elicited a transient systemic cytokine response and enhanced systemic tumor-specific T-cell responses. Conclusions: Single intratumoral injection of C. novyi-NT is feasible. Toxicities can be significant but manageable. Signals of antitumor activity and the host immune response support additional studies of C. novyi-NT in humans.