TuHURA and Kintara Announce Positive Phase 1b Results for IFx-2.0

TuHURA Biosciences and Kintara Therapeutics have announced promising results from a Phase 1b trial of IFx-2.0, a cancer vaccine aimed at patients with advanced or metastatic Merkel Cell Carcinoma (MCC) or Cutaneous Squamous Cell Carcinoma (cSCC) who have shown resistance to immune checkpoint inhibitors (ICIs). The findings were presented at the 2024 American Society of Clinical Oncology (ASCO) Annual Meeting.

The study revealed that IFx-2.0 was safe and well tolerated when administered once weekly for three weeks. Notably, 80% of patients with advanced MCC who had not previously responded to therapies like pembrolizumab or avelumab achieved a sustained Complete Response (CR), pathologic CR, or Partial Response (PR) after undergoing IFx-2.0 treatment and a rechallenge with an anti-PD(L)-1 checkpoint inhibitor.

Dr. James Bianco, CEO of TuHURA, expressed optimism about the results, highlighting that IFx-2.0 managed to overcome resistance to ICIs in 63% of patients with advanced MCC. These patients had previously failed multiple lines of therapy, including anti-PD1 and anti-CTLA-4 combination treatments, as well as chemotherapy and other investigational agents.

The study focused on a specific group of seven patients with ICI-naïve, advanced MCC who had not received any systemic or investigational therapies before IFx-2.0 treatment. Five of these patients progressed within 3.8 months on single-agent anti-PD(L)-1 therapy. Following IFx-2.0 treatment and rechallenge with an anti-PD(L)-1 agent, four of these five patients achieved a durable objective response lasting an average of 25 months. Two responses were ongoing at 19 and 23 months. Another patient among the remaining two achieved a partial response, which continued for six months post rechallenge with an anti-PD-1 agent.

Based on these promising initial results, TuHURA is planning a Phase 3 clinical trial to evaluate IFx-2.0 as an adjunctive therapy with Keytruda® (pembrolizumab) in first-line treatment for ICI-naïve patients with advanced or metastatic MCC. The Phase 3 trial is scheduled to begin enrollment in the second half of 2024, under the FDA's Accelerated Approval Pathway.

TuHURA's IFx-2.0 is a personalized cancer vaccine that involves injecting a small amount of plasmid DNA (pDNA) into a patient's tumor. This pDNA encodes an immunogenic bacterial protein designed to make the tumor's surface resemble a bacterium, thereby priming the patient's innate immune response against the tumor. This innovative approach aims to harness the body's natural immune mechanisms to recognize and attack cancer cells.

The primary goal of the Phase 1b study was to establish the safety and feasibility of repeated administrations of IFx-2.0, which was successfully met. An exploratory analysis showed that 63% of MCC patients treated with IFx-2.0 and subsequently rechallenged with ICIs experienced durable disease control, indicating a potential “immune priming” effect.

This new development has set the stage for a randomized study of pembrolizumab with or without IFx-2.0 in the first-line treatment of advanced MCC. The study’s promising efficacy signals have been a driving force behind TuHURA's planned Phase 3 trial.

TuHURA has also entered into an all-stock transaction with Kintara to combine resources and expertise to advance their oncology pipeline. The combined company will focus on developing TuHURA's personalized cancer vaccines and bi-functional Antibody Drug Conjugates (ADCs) to overcome the limitations of current cancer immunotherapies. This merger is expected to close in the third quarter of 2024, pending customary closing conditions and stockholder approvals.