Scancell iSCIB1+ Phase III: Regulatory Green Light, But No Efficacy Data Behind a High-Bar Triplet Bet

Scancell Secures UK MHRA Approval for Phase III Melanoma Trial

Scancell Holdings has received Clinical Trial Authorisation (CTA) from the UK Medicines and Healthcare products Regulatory Agency (MHRA) for a Phase III registrational trial of its ImmunoBody, iSCIB1+, for advanced melanoma. The placebo-controlled, double-blind, randomised study will enroll 550 participants with stage III or IV unresectable melanoma across approximately 90 sites globally. Patients will receive 8mg iSCIB1+ in combination with ipilimumab and nivolumab, or placebo plus checkpoint inhibitors. The primary endpoint is progression-free survival (PFS), with overall survival (OS) as a secondary endpoint, aiming for accelerated and full approval, respectively. This follows US FDA IND clearance in January 2026.

• Scancell has achieved significant regulatory progress, securing Clinical Trial Authorisation from the UK MHRA for its Phase III trial of iSCIB1+ in advanced melanoma. This follows the US FDA's clearance of an Investigational New Drug (IND) application in January 2026. The company anticipates initiating the trial by the end of 2026, with initial progression-free survival (PFS) data expected in the second half of 2028.
• The Phase III study is a placebo-controlled, double-blind, randomised trial designed to enroll 550 participants with stage III or IV unresectable melanoma. It will be conducted across approximately 90 sites in Australia, Canada, the EU, the UK, and the US. Patients will be randomised 1:1 to receive either 8mg iSCIB1+ in combination with ipilimumab and nivolumab, or a placebo alongside the same checkpoint inhibitors.
• The trial's primary endpoint is progression-free survival (PFS), intended to support a submission for accelerated regulatory approval. Overall survival (OS) is a key secondary endpoint, which may support an application for full approval at a later stage. This design is informed by positive data from the previous Phase II SCOPE trial, where iSCIB1+ combined with ipilimumab and nivolumab demonstrated a sustained PFS rate of 77% after 22 months and an OS rate of 87.4% at 18 months in the targeted population.

Addressing Persistent Challenges in Advanced Melanoma Treatment

Advanced melanoma treatment has advanced substantially over the past decade, yet several clinically significant barriers continue to limit durable outcomes across patient populations. The following challenges represent critical unmet needs that shape ongoing research and therapeutic strategy.

• Acquired resistance to MAPK-targeted therapy: The majority of patients treated with MAPK inhibitors develop acquired resistance at approximately 12 months. Resistance mechanisms are diverse and include reactivation of the MAPK pathway with sustained ERK signaling, as well as activation of parallel oncogenic pathways such as PI3K–mTOR. The p53 pathway has also been implicated as a contributor to resistance against targeted MAPK inhibition.

• Brain metastases and CNS penetration: Melanoma carries the highest propensity among solid tumors to metastasize to the brain, yet patients with melanoma brain metastases (MBM) are routinely excluded from clinical trials, resulting in a critical evidence gap. The blood-brain barrier limits the efficacy of systemic therapies, and the pathophysiology underlying melanoma cell extravasation, interaction with the CNS microenvironment, and transcriptomic adaptation to brain-specific cues remains poorly characterized.

• Immune-related adverse events (irAEs): A substantial proportion of patients receiving immune checkpoint inhibitors experience irAEs — including colitis/diarrhea, dermatitis, hepatitis, endocrinopathies, uveitis, nephritis, and inflammatory myopathy — that necessitate systemic corticosteroid management. Corticosteroids can attenuate the anti-tumoral immune response and may negatively impact survival outcomes. The combination of CTLA-4 and PD-1 inhibitors, while clinically active, is associated with a markedly increased irAE burden.

• Immune checkpoint resistance mechanisms: Beyond irAEs, intrinsic and acquired resistance to checkpoint blockade represents a distinct therapeutic challenge. Upregulation of the negative immune checkpoint regulator VISTA has been identified as a potential mechanism of acquired resistance in patients treated with anti-PD-1 therapy. Additional resistance drivers include downregulation of HLA-associated antigen presentation pathways and alterations in immune cell responsiveness to melanoma cells undergoing targeted therapy — collectively undermining durable immunological control.

Key Design Elements of the iSCIB1+ Phase III Trial

The following pivotal Phase III (and select Phase II) trials have established the benchmark efficacy and safety data against which emerging agents in advanced melanoma are evaluated. Across these studies, overall survival and progression-free survival serve as the primary endpoints, with randomized, controlled designs enabling direct or indirect comparisons across immunotherapy and targeted therapy regimens.

iSCIB1+ in the Evolving Combination Therapy Landscape

Combination therapy strategies in advanced melanoma have expanded considerably, with recent trials exploring synergistic approaches across immune checkpoint inhibition, targeted therapy, and intratumoral immunotherapy. These combinations aim to improve upon the efficacy of monotherapy while managing the trade-offs in tolerability. The evolving landscape offers a range of mechanistic rationales that may inform how novel agents such as iSCIB1+ could be positioned.

• Dual ICI combinations: Nivolumab plus ipilimumab (PD-1/CTLA-4 co-blockade) has demonstrated the longest overall survival reported in advanced melanoma, including in BRAF-mutant populations, though durable responses come with a significant burden of severe immune-related toxicity. The newer LAG-3/PD-1 dual blockade regimen of nivolumab-relatlimab has emerged as a compelling alternative, with real-world data reporting an overall response rate of 39% and notable PFS improvements — particularly in first-line patients — alongside a more favorable safety profile.

• BRAF/MEK inhibition combined with anti-PD-1 therapy: The IMPemBra trial evaluated pembrolizumab (200 mg Q3W) with intermittent or short-term dabrafenib plus trametinib in BRAF-mutant melanoma. Patients randomized to intermittent dabrafenib/trametinib schedules (ranging from one-week cycles to a continuous six-week course) demonstrated that intermittent triple therapy was more feasible and tolerable than continuous dosing, with efficacy signals appearing favorable over pembrolizumab monotherapy.

• Intratumoral immunotherapy combinations: Intratumoral agents including T-VEC, CAVATAK, HF10, and TLR9 agonists have demonstrated improved response rates when combined with immune checkpoint inhibitors relative to monotherapy. Additionally, intratumoral IFN-γ and topical TLR7 agonist (imiquimod) have been shown to promote infiltration of melanoma metastases by vaccine-induced circulating T lymphocytes, enhancing T-cell–mediated tumor control when used alongside cancer vaccine strategies.

Scancell's iSCIB1+ Enters Phase III: Redefining Advanced Melanoma Treatment

The initiation of Scancell's Phase III registrational trial for iSCIB1+ in advanced melanoma marks a pivotal moment in immuno-oncology, signaling a strategic push to enhance the efficacy of established checkpoint inhibitor therapies. While agents like nivolumab, particularly in combination with ipilimumab, have revolutionized the treatment landscape for unresectable stage III or IV melanoma, a significant proportion of patients still face disease progression or recurrence. This trial aims to address that critical unmet need by integrating a novel T-cell activating vaccine, iSCIB1+, with the current standard of care.

iSCIB1+ is designed to stimulate both CD4+ T-helper and CD8+ cytotoxic T-cell responses against tumor-associated antigens such as gp100 and TRP-2. Research has consistently shown that coactivating CD4+ T-helper cells can significantly augment CD8+ T-cell responses, leading to improved clinical outcomes. By introducing a broad and potent anti-tumor immune response, iSCIB1+ seeks to:

• Deepen and prolong the anti-tumor effects initiated by checkpoint blockade.

• Potentially overcome mechanisms of resistance to existing immunotherapies.

• Broaden the patient population that can benefit from immunotherapy.

However, the path forward is not without its complexities. Studies with the precursor SCIB1 vaccine have indicated that generating robust T-cell responses can be more challenging in patients with established tumors compared to those without, suggesting that the advanced disease microenvironment may present an immunological hurdle. Furthermore, the optimal combination of immune checkpoint inhibitors is still being explored, and introducing a third agent, particularly a vaccine, necessitates careful monitoring for potential synergistic toxicities or novel immune-related adverse events. The high efficacy bar set by nivolumab and ipilimumab combination therapy means iSCIB1+ must demonstrate a clear and meaningful clinical benefit to justify its integration into treatment protocols. If successful, this trial could not only redefine the treatment paradigm for advanced melanoma but also validate the broader potential of therapeutic vaccines in combination with checkpoint inhibitors across oncology.