KEYTRUDA QLEX: First-Mover SC Checkpoint Inhibitor in Japan, But Convenience Without Survival Edge Tests Payer Logic

Japan Approves Merck's Subcutaneous KEYTRUDA QLEX

Merck announced that KEYTRUDA QLEX (pembrolizumab and berahyaluronidase alfa-pmph) injection for subcutaneous use has been approved by the MHLW in Japan for all indications currently approved for intravenous KEYTRUDA. This makes KEYTRUDA QLEX the first and only subcutaneous immune checkpoint inhibitor in Japan, offering administration in as little as one minute. The approval is supported by the pivotal Phase 3 MK-3475A-D77 trial in treatment-naïve metastatic non-small cell lung cancer, which demonstrated comparable pharmacokinetic exposure and consistent overall response rates (45% for KEYJECT with chemotherapy vs. 42% for KEYTRUDA with chemotherapy), with no notable differences in progression-free or overall survival.

• The Ministry of Health, Labor and Welfare (MHLW) in Japan has granted approval for KEYTRUDA QLEX, a subcutaneous formulation of pembrolizumab, for all existing indications of intravenous KEYTRUDA. This significant regulatory achievement positions KEYTRUDA QLEX as the first and only subcutaneous immune checkpoint inhibitor available in Japan, enhancing patient access and convenience with rapid administration options.
• The approval is underpinned by data from the Phase 3 MK-3475A-D77 trial, which evaluated KEYTRUDA QLEX against intravenous KEYTRUDA in patients with treatment-naïve metastatic non-small cell lung cancer. The study successfully demonstrated comparable pharmacokinetic exposure levels between the subcutaneous and intravenous formulations, confirming the bioequivalence of the new delivery method.
• Beyond pharmacokinetic comparability, descriptive analyses from the MK-3475A-D77 trial showed consistent overall response rates (ORR) between KEYTRUDA QLEX (45%) and intravenous KEYTRUDA (42%) when combined with chemotherapy. Furthermore, no notable differences were observed in progression-free survival (PFS) and overall survival (OS), reinforcing the therapeutic equivalence of the subcutaneous formulation to the established intravenous therapy.

Streamlining KEYTRUDA Administration: Addressing Patient and Provider Needs

NSCLC treatment has advanced considerably with the introduction of immune checkpoint inhibitors (ICIs) and targeted therapies, yet significant clinical and biological barriers continue to limit durable outcomes. Resistance — whether primary or acquired — remains a central challenge across both immunotherapy and targeted therapy paradigms.

• Immunotherapy resistance driven by tumor microenvironment and genetic factors: The immunosuppressive tumor microenvironment (TME), characterized by regulatory T cells and myeloid-derived suppressor cells, can hinder ICI efficacy. Key genetic alterations associated with resistance include STK11, KEAP1, and EGFR mutations, particularly in the context of low tumor mutational burden (TMB). Metabolic alterations and deficient antigen presentation further contribute to resistance, and prior treatments can alter the TME, affecting subsequent immunotherapy responses.

• Limitations of current biomarkers for immunotherapy response: TMB and PD-L1 expression remain imperfect predictors of ICI response. In SCLC — closely related to NSCLC in treatment paradigm overlap — TMB and PD-L1 do not serve as reliable biomarkers of ICB response. In NSCLC, high TMB has been associated with low B2M expression, which may explain the poor predictive value of TMB in some situations. High levels of B2M mRNA, but not PD-L1, are correlated with an enhanced response to PD-1-based immunotherapy, underscoring the inadequacy of current standard biomarkers.

• Acquired resistance to EGFR-targeted therapies: Patients with EGFR-activating mutated NSCLC treated with EGFR tyrosine kinase inhibitors (TKIs) ultimately develop acquired resistance (AR). Among known cases, 70% of AR mechanisms have been identified and may be categorised as secondary EGFR mutations (such as T790M), activation of bypass track signalling pathways (such as MET amplification), or histologic transformation. Even third-generation EGFR-TKIs such as osimertinib, approved for T790M-positive NSCLC, face acquired resistance after approximately 10 months, driven by heterogeneous mechanisms including new EGFR mutations, HER2 or MET amplification, and histological transformation to SCLC.

• Dual resistance mechanisms in combination targeted therapy: In MET-amplified, EGFR-TKI-resistant NSCLC, concurrent EGFR-TKI and MET-TKI treatment can itself drive further resistance. Distinct bypass signalling mechanisms — including IGF/IGF1 receptor activation and HSP90-mediated MET stabilisation — have been identified across resistant clones, highlighting the complexity of overcoming multi-pathway resistance in this population.

• Immune-related adverse events (irAEs) with ICI therapy: While PD-1/PD-L1 inhibitors are generally better tolerated than chemotherapy — with significantly lower risk of fatigue, sensory neuropathy, diarrhea, hematologic toxicities, and treatment discontinuation — they generate a unique spectrum of irAEs. These include increased risk of all-grade rash, pruritus, colitis, hypothyroidism, hyperthyroidism, ALT/AST elevations, and all- and high-grade pneumonitis, several of which can be severe and life-threatening, with potential negative impact on patients' quality of life and survival outcomes.

• Limited efficacy of novel combination strategies in unselected populations: The combination of the CXCR2 antagonist navarixin with pembrolizumab in previously treated advanced NSCLC yielded an objective response rate of 0% in the NSCLC cohort, with median progression-free survival of 1.8–2.4 months and no evidence of a dose-response relationship, leading to study closure at a prespecified interim analysis for lack of efficacy. This underscores the challenge of translating preclinical rationale into clinical benefit without robust patient selection strategies.

Pivotal MK-3475A-D77 Trial: Supporting KEYJECT's Broad Approval

Several pivotal trials have evaluated systemic therapies across the NSCLC spectrum, spanning targeted agents, immunotherapy combinations, and novel antibody-drug conjugate strategies. The studies below represent a range of designs — from phase I/II integrated analyses to phase III randomized controlled trials — each with distinct patient populations, stratification approaches, and endpoint hierarchies.

Safety and Tolerability Profile of Subcutaneous KEYTRUDA QLEX

Berahyaluronidase alfa is identified as one of the recombinant hyaluronidases used in hyaluronidase-facilitated subcutaneous (SC) formulation development for oncology antibodies, including pembrolizumab. In pivotal bridging trials evaluating SC regimens, safety profiles were broadly similar to intravenous (IV) comparators. SC administration was associated with fewer administration-related reactions for several agents, while injection-site reactions were generally mild. Immunogenicity — including anti-hyaluronidase antibodies — did not show consistent clinically meaningful effects on pharmacokinetics or outcomes.

Across the broader pembrolizumab safety literature, immune-related adverse event (irAE) profiles vary by indication and treatment context. In a real-world cohort of 100 patients with early-stage triple-negative breast cancer receiving neoadjuvant chemotherapy combined with pembrolizumab, 61% experienced at least one irAE, with 30% of those being grade 3–5, including one grade 5 immune-related myocarditis. Treatment discontinuation due to adverse events in the neoadjuvant phase was 35%, and 50% of patients required dose reductions of at least one chemotherapy drug — rates described as higher than those documented in the pivotal KEYNOTE-522 trial. In patients with recurrent or metastatic head and neck squamous-cell carcinoma treated with pembrolizumab plus nab-paclitaxel and platinum, grade ≥3 treatment-related adverse events included leukopenia (26.7%), neutropenia (26.7%), peripheral neurotoxicity (3.3%), rash (3.3%), hyperalgesia (3.3%), and immune-related pneumonitis (3.3%), with hypothyroidism being the most common irAE at 40.0%.

A meta-analysis of 8,730 patients from clinical trials comparing anti-PD-1 and anti-PD-L1 monotherapy found that pembrolizumab carried a higher risk of any-grade irAEs relative to atezolizumab, and a higher risk of grade ≥3 irAEs relative to avelumab, though findings were characterized as hypothesis-generating. In non-small cell lung cancer patients with HIV receiving pembrolizumab or nivolumab, none experienced grade 3 or 4 irAEs, and none required dose interruption or discontinuation due to toxicity. The knowledge base does not have sufficient information on this aspect regarding safety and tolerability data specific to the pembrolizumab and berahyaluronidase alfa-pmph SC formulation across its full range of studied indications beyond the bridging trial-level observations noted above.

KEYTRUDA QLEX: Redefining Immuno-Oncology Delivery in Japan

The recent approval of KEYTRUDA QLEX in Japan represents a pivotal moment for immuno-oncology, ushering in the era of subcutaneous (SC) immune checkpoint inhibitor (ICI) therapy. As the first and only SC ICI in the country, this development significantly enhances the patient experience, offering administration in as little as one minute compared to the longer intravenous (IV) infusion times. This convenience is not merely a comfort factor; it has profound implications for patient access, adherence, and overall quality of life, potentially reducing the burden of frequent clinic visits.

The approval is robustly supported by clinical data demonstrating comparable pharmacokinetic exposure and consistent efficacy, including overall response rates, progression-free survival, and overall survival, to the IV formulation in metastatic non-small cell lung cancer. Crucially, this SC formulation is approved for all indications currently held by IV KEYTRUDA, a testament to the successful model-based pharmacokinetic bridging that confirms its applicability across diverse tumor types and treatment settings. This broad approval underscores a strategic move to solidify pembrolizumab's market leadership and extend its lifecycle.

However, as with any innovation, there are considerations. While generally mild, SC administration is known to be associated with a higher incidence of local injection site reactions compared to IV delivery. Furthermore, while low, the potential for anti-drug antibody development, a known risk with biologic therapies, warrants ongoing monitoring. From a broader healthcare perspective, while the convenience is undeniable, the literature indicates that the SC formulation 'remains expensive.' This necessitates careful consideration of pricing strategies and the potential implementation of cost-saving dosing regimens, such as extended intervals or body-weight-adjusted approaches, to ensure equitable access and long-term sustainability within healthcare systems. This approval sets a new standard, compelling the industry to innovate further in drug delivery while balancing patient needs, clinical outcomes, and economic realities.