Tudriqev's FDA Win Reopens Oncolytic Virus Category, But Imlygic's Commercial Ghost Looms Large

Replimune's Tudriqev Approval Signals New Era for Localized Cancer Therapies

The article discusses the potential of locally delivered cancer therapeutics, exemplified by Replimune’s recently approved Tudriqev and Amgen’s Imlygic. Replimune’s Tudriqev, an oncolytic virus for melanoma, received FDA approval last month, marking only the second such approval for a directly injected oncolytic virus. While Amgen’s Imlygic, approved in 2015 for unresectable melanoma, had modest sales, experts believe newer localized treatments like Tudriqev could achieve significant sales, with BMO Capital Markets estimating $1.3 billion annually by 2035. These therapies are seen as advantageous for earlier treatment, leveraging surgery, and potentially improving safety by reducing systemic toxicity. Despite challenges in commercialization and regulation, the field is rapidly evolving, with a "tipping point" expected in the next five years.

• The Promise of Localized Delivery: Locally delivered therapeutics, such as Replimune's Tudriqev and Amgen's Imlygic, offer significant advantages by directly targeting tumors. This approach is particularly beneficial for early-stage cancer, allowing for the immune system to be activated when the tumor is more vulnerable. Experts like Michael Goldberg of Surge Therapeutics emphasize how intraoperative immunotherapy can transform surgery into a therapeutic intervention, addressing the high rates of recurrence and metastasis.
• Improved Safety and Efficacy Profile: Local delivery mechanisms can enhance the safety and efficacy balance of cancer treatments. By administering drugs directly into the tumor, higher concentrations can be achieved at the target site with lower systemic doses, thereby reducing severe, life-threatening toxicities often associated with systemic administration. Ankyra Therapeutics' ANK-101, for instance, uses an aluminum hydroxide scaffold to keep 99% of the IL-12 cytokine within the tumor, allowing for effective responses with fewer safety issues.
• Commercial and Regulatory Landscape: Despite the clinical promise, the commercial landscape for intratumoral therapies remains largely unexplored, and regulatory pathways can be challenging, as evidenced by Replimune's "perilous regulatory road." While past sales of drugs like Imlygic have been modest due to limitations in use (e.g., only for unresectable tumors), industry leaders believe that expanding the use of these drugs to earlier stages of disease could significantly broaden their market share and commercial potential, with projections like $1.3 billion annually for Tudriqev by 2035.

Addressing Melanoma's Unmet Needs with Localized Delivery

Despite significant therapeutic advances in advanced melanoma, substantial clinical challenges persist across both targeted therapy and immunotherapy paradigms. Resistance, toxicity, and incomplete efficacy in specific disease compartments continue to limit durable patient benefit.

• Acquired resistance to BRAF and MEK inhibitors: Vemurafenib and other BRAF inhibitors are limited by the development of acquired resistance, primarily driven by MAPK pathway reactivation through secondary mutations in NRAS (Q61) and MEK1 (Q56P, E203K). Cross-resistance between BRAF and MEK inhibitors is common, except when resistance arises from secondary NRAS mutations. Persistence or induction of AKT pathway activity further compounds resistance, and while combination RAF/MEK inhibition with AKT or mTOR inhibitors has shown potential to reverse this, clinical translation remains an active area of investigation.

• Limited and short-lived efficacy in melanoma brain metastases (MBM): Single-agent BRAF inhibitors achieve intracranial response rates of only 25% to 40%, and while BRAFi/MEKi combinations improve this to up to 58%, the durability of responses in MBM appears even shorter than in extracranial disease. Although CTLA-4 and PD-1/PD-L1 checkpoint inhibitors have demonstrated activity — with the CTLA-4 + PD-1 antibody combination inducing durable responses at a rate of 55% — the optimal sequencing and combination of systemic and local therapies (surgery, radiotherapy) in MBM remains undefined.

• Acquired resistance to anti-PD-1 immunotherapy: Among patients who initially respond to anti-PD-1 therapy, resistance mechanisms include significantly increased density of VISTA+ lymphocytes, elevated tumor PD-L1 expression, increased intratumoral FOXP3+ lymphocytes, and loss of tumor PTEN and downregulation of HLA-A and HLA-DPB1. Enhanced IL-34 expression in refractory metastatic melanoma, correlating with increased CD163 macrophage frequencies, has also been identified as a potential resistance mechanism. Only 20–40% of metastatic melanoma patients experience long-term benefit from anti-PD-1 agents such as pembrolizumab and nivolumab.

• Immune-related adverse events (irAEs) and treatment discontinuation: Checkpoint inhibitor therapy is associated with a broad spectrum of irAEs — including pneumonitis, colitis, hepatitis, myocarditis, nephritis, and endocrinopathies — that frequently necessitate suspension or discontinuation of treatment and, in rare instances, may lead to fatalities. Co-occurring infections in patients receiving checkpoint inhibitors significantly increase the risk of irAEs. Recurrent pneumonitis, including unprovoked recurrence following complete drug discontinuation, represents a particularly poorly characterized and potentially fatal complication requiring closer monitoring and prolonged steroid treatment.

• Absence of consensus on treatment sequencing and second-line strategies: In clinical practice, there is no single preferred agent for second-line treatment of either BRAF mutant or BRAF wild-type advanced melanoma. Most sequencing has historically moved from dacarbazine to newer agents such as ipilimumab and vemurafenib, but the rapid evolution of the treatment landscape has outpaced the establishment of evidence-based sequencing guidelines across European and broader clinical settings.

The Evolving Landscape and Future of Intratumoral Oncology

The past decade has seen melanoma treatment transformed by two converging therapeutic pillars: immune checkpoint inhibitors (ICIs) and BRAF/MEK-targeted therapies. In the metastatic setting, PD-1 inhibitors — pembrolizumab and nivolumab — have supplanted chemotherapy and ipilimumab monotherapy as standards of care, delivering superior progression-free survival and overall survival. The dual ICI combination of nivolumab plus ipilimumab has produced the most durable outcomes in advanced disease, with 10-year final data from CheckMate 067 revealing survival plateaus extending beyond seven years in approximately 31% of combination-treated patients. For BRAF V600E/K-mutant metastatic melanoma, the 7-year update of the COLUMBUS trial demonstrated that encorafenib plus binimetinib achieved a 7-year overall survival rate of 27.4% and a median melanoma-specific survival of 36.8 months, compared with 18.2% and 19.3 months, respectively, for vemurafenib — the longest follow-up reported from a phase III BRAF/MEK inhibitor trial in this population. Emerging data also support nivolumab plus relatlimab (dual LAG-3 and PD-1 blockade) as a promising option with a favorable toxicity profile relative to nivolumab-ipilimumab, though mature survival data remain pending.

Perhaps the most consequential recent shift has been the establishment of neoadjuvant immunotherapy as superior to adjuvant therapy alone in clinically detectable stage III disease. A randomized trial demonstrated that event-free survival was significantly improved with neoadjuvant pembrolizumab compared to standard surgery followed by adjuvant therapy, with high pathologic response rates driving this benefit. Data from the NADINA trial further support a compelling neoadjuvant role for nivolumab-ipilimumab combination. BRAF/MEK inhibition in the neoadjuvant setting has also shown high pathologic response rates, though these appear less durable than those achieved with immunotherapy. These findings have collectively reshaped treatment algorithms, positioning neoadjuvant therapy as the new standard of care for locoregionally advanced melanoma.

In the adjuvant setting, ICIs and BRAF/MEK inhibitors have replaced interferon-α, demonstrating improvements in recurrence-free survival and the emergence of long-term survivors across high-risk resected populations. However, important nuances persist: the adjuvant CheckMate 915 trial failed to demonstrate a recurrence-free survival benefit for nivolumab-ipilimumab over nivolumab monotherapy, and prior treatment with BRAF inhibitors has been associated with significantly lower median progression-free survival (3 months versus not reached) and disease control rates (18.6% versus 65.4%) upon subsequent pembrolizumab therapy — underscoring that treatment sequencing carries meaningful clinical consequences. Overcoming resistance mechanisms and refining sequencing strategies remain central challenges as the field moves toward biomarker-driven, personalized approaches.

Oncolytic Viruses: A New Horizon for Localized Immunotherapy

The recent FDA approval of Replimune’s Tudriqev marks a pivotal moment for the field of oncolytic viral therapy, signaling a potential "tipping point" for localized cancer treatments. This approval, following Amgen’s Imlygic (talimogene laherparepvec or T-VEC) in 2015, underscores a growing confidence in the therapeutic potential of viruses engineered to selectively target and destroy cancer cells while simultaneously stimulating the body's immune system.

T-VEC, the first oncolytic immunotherapy, demonstrated that these agents can achieve durable response rates and improve overall survival in patients with unresectable melanoma, particularly in earlier stages, with a favorable safety profile. Its mechanism involves direct tumor cell lysis and the release of tumor antigens, coupled with GM-CSF expression to enhance local and systemic anti-tumor immune responses. However, studies indicated that T-VEC monotherapy had a mild systemic effect, especially in patients with visceral metastases, highlighting the need for combination strategies.

Newer oncolytic viruses, such as Tudriqev, are emerging from advanced platforms designed to optimize tumor cell killing and immunogenicity. Research shows that modifications like fusion-enhanced herpes simplex virus type 1 (HSV-1) can augment oncolytic ability and lead to enhanced immunogenic cell death, potentially generating stronger systemic anti-tumor effects. This evolution suggests next-generation oncolytic viruses could offer improved efficacy, particularly when combined with immune checkpoint inhibitors (ICIs). Replimune's strategic implication is to position Tudriqev as a superior, combination-ready therapy, building on T-VEC's foundational understanding.

However, the path forward is not without challenges. A key risk lies in demonstrating robust systemic efficacy, especially in combination with ICIs, to overcome prior monotherapy limitations. Commercialization hurdles, evidenced by Imlygic's modest sales, also need careful navigation, requiring effective physician education and streamlined administration. Furthermore, ongoing research must address systemic delivery and immune clearance to unlock the full potential of oncolytic viruses in widespread metastatic disease. Despite these considerations, Tudriqev's approval reinforces the strategic importance of intralesional therapies, promising to expand treatment options and improve outcomes for patients with melanoma and potentially other solid tumors.