Amaria, Rodabe N.

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.

Clinical stage III melanoma, defined as resectable RECIST measurable nodal disease with or without in-transit metastases, represents approximately 15% of new melanoma diagnoses every year with additional cases presenting as recurrent nodal disease following previous treatment of a primary melanoma. The standard of care for patients with resectable clinical stage III melanoma is surgical resection, consisting of therapeutic lymph node dissection and/or resection of in-transit disease and consideration of adjuvant systemic therapy and occasionally adjuvant radiation. These patients have high rates of regional recurrence and progression to metastatic disease postsurgery, highlighting the need for better treatment options. With the success of immune checkpoint inhibitors in both the adjuvant and metastatic settings, the use of these agents in the neoadjuvant setting has been an emerging area of research interest. In this chapter, we will discuss the rationale for neoadjuvant immunotherapy; review impactful clinical trials; and define response monitoring, surgical considerations, emerging therapies, and unanswered questions for neoadjuvant therapy as a recent paradigm shift in the management of clinical stage III melanoma.