Primmune Secures $23.3M to Advance Novel Melanoma Immunotherapy

SAN DIEGO, Jan. 26, 2026 – Primmune Therapeutics, a clinical-stage biotech company focused on the innate immune system, has bolstered its financial position with an additional $8.6 million close of its Series B financing. The move, supported by investors Bioqube Ventures, Oberland Capital, and Samsara Biocapital, brings the round's total to $23.3 million and is set to propel the company’s lead candidate, PRTX007, into a pivotal Phase 2 clinical trial for melanoma.

The funding will directly support the initiation of a neoadjuvant study for patients with Stage III resectable melanoma, combining the novel oral immunotherapy with standard-of-care anti-PD-1 therapy. This step marks a critical milestone for a drug designed to overcome the historical limitations of its class, potentially offering a new, more tolerable weapon in the fight against solid tumors.

A New Approach to Innate Immunity

At the heart of Primmune's strategy is PRTX007, a small molecule designed to precisely harness the power of the innate immune system. It belongs to a class of drugs known as toll-like receptor 7 (TLR7) agonists, which work by activating a key sentinel of the immune system. For years, the therapeutic promise of systemically-acting TLR7 agonists has been hampered by a significant drawback: severe, dose-limiting toxicity. Previous attempts often resulted in a "cytokine storm," a dangerous overproduction of pro-inflammatory molecules like IL-6 and TNFα, driven by a signaling pathway known as NF-κB.

Primmune believes it has engineered a solution. PRTX007 is designed to selectively activate a different branch of the TLR7 pathway, one governed by interferon regulatory factor 7 (IRF7). This targeted activation triggers a robust and therapeutically beneficial poly-interferon response, which is crucial for anti-tumor and antiviral activity, while sidestepping the NF-κB-mediated inflammation that has plagued its predecessors. In essence, the drug aims to provide the benefits of a powerful interferon cocktail without the associated systemic toxicity.

Data from two completed Phase 1 studies in over 100 healthy volunteers appear to support this unique profile. The drug was generally well-tolerated, with no serious adverse events reported. Crucially, while pharmacodynamic data showed the desired systemic activation of key anti-tumor immune cells—including CD8+ T cells and NK cells—there were no corresponding systemic increases in pro-inflammatory cytokines. This carefully tuned immune response suggests PRTX007 could be a safer and more effective partner for other immunotherapies.

Investor Confidence in a Competitive Landscape

Securing a $23.3 million Series B round is a significant achievement in the competitive and often challenging biotech funding environment. The participation of specialist life science investors like Bioqube Ventures, Oberland Capital, and Samsara Biocapital underscores a strong belief in Primmune's differentiated scientific platform and its potential clinical and commercial value.

These are not generalist investors; their portfolios demonstrate a deep understanding of the oncology and immunology landscape. Samsara Biocapital, for instance, has a track record of backing companies developing next-generation cancer treatments, including novel T-cell and NK cell therapies. Their investment in Primmune signals confidence that PRTX007's unique mechanism of action represents a tangible advancement in the field of immunotherapy.

The capital injection provides Primmune with the runway needed to generate crucial human proof-of-concept data. “This financing enables us to rapidly advance PRTX007 into a clearly defined proof-of-principle study with validated efficacy and safety endpoints, with the goal of establishing PRTX007 as a class-leading immunotherapy option for patients with solid tumors,” said Charlie McDermott, Chief Executive Officer and Director of Primmune Therapeutics, in a statement.

Targeting Melanoma in a Pivotal Neoadjuvant Study

The new funds will be immediately deployed to launch Study PRTX007-003, a Phase 2 trial with a modern and promising design. The study will evaluate PRTX007 in a neoadjuvant setting—meaning the treatment is administered before surgery—for patients with Stage III resectable melanoma. This approach has gained significant traction in oncology, as pre-surgical treatment can shrink tumors, making them easier to remove, and can help prime a systemic immune response to eliminate micrometastases, potentially reducing the risk of recurrence.

Patients in the trial will receive PRTX007 in combination with an existing standard-of-care treatment: an anti-PD-1 immune checkpoint inhibitor (ICI). ICIs have revolutionized melanoma treatment by "releasing the brakes" on the immune system, but not all patients respond, and many eventually relapse. The scientific rationale for the combination is compelling: PRTX007 acts as an immune system "accelerator," activating the innate immune response and priming T-cells, which could then be more effectively unleashed by the anti-PD-1 therapy. This synergy aims to improve response rates and create more durable anti-tumor immunity in a high-risk patient population.

The Australian Advantage in Clinical Development

In a strategic move that reflects a growing global trend, Primmune will conduct the entire Phase 2 study in Australia through its subsidiary, Primmune Therapeutics Pty Ltd., in partnership with the clinical research organization Novotech. The decision highlights Australia's emergence as a premier destination for early-stage clinical trials.

This choice is driven by several key benefits, collectively known as "the Australian Advantage." The country's regulatory framework, governed by the Therapeutic Goods Administration (TGA), features a Clinical Trial Notification (CTN) scheme that allows studies to commence within weeks of receiving ethics approval, a timeline significantly faster than in the U.S. or Europe.

Furthermore, the Australian government offers one of the world's most generous R&D tax incentive programs. For eligible companies, the program provides a refundable tax offset of up to 43.5% on R&D expenditures, which for an early-stage company like Primmune translates into a substantial non-dilutive cash rebate. This financial incentive dramatically reduces the net cost of conducting a trial, allowing venture capital to go further. Combined with a world-class research infrastructure, experienced investigators, and high data quality standards, Australia offers an environment where Primmune can execute its pivotal study efficiently and cost-effectively, accelerating the development of what could be a vital new therapy for cancer patients.