RAHWAY, N.J. – September 20, 2025 — Merck (NYSE: MRK) announced that the U.S. Food and Drug Administration (FDA) has approved KEYTRUDA® QLEX™ (pembrolizumab and hyaluronidase alfa-pmph) injection for subcutaneous (SC) administration across most adult solid tumor indications where intravenous (IV) KEYTRUDA® is currently approved. This marks a significant regulatory milestone, allowing the first subcutaneous PD-1 inhibitor option for patients with multiple solid tumor cancers.
Science Significance
KEYTRUDA QLEX is a co-formulation of pembrolizumab, Merck’s anti–PD-1 antibody, with recombinant human hyaluronidase alfa. Hyaluronidase enables rapid absorption of large molecules through subcutaneous tissue, allowing pembrolizumab—normally infused intravenously over 30 minutes—to be administered via a short injection under the skin. Clinical data from the pivotal Phase 3 KEYNOTE-D77 trial demonstrated pharmacokinetic equivalence, comparable efficacy, and a consistent safety profile between SC QLEX and standard IV KEYTRUDA across multiple tumor types. This innovation represents a major advance in drug delivery technology, improving convenience without compromising the well-established clinical benefits of PD-1 inhibition.
Regulatory Significance
The FDA approval covers all adult solid tumor indications where IV KEYTRUDA is approved, including non–small cell lung cancer, melanoma, renal cell carcinoma, head and neck squamous cell carcinoma, and others. This is the first FDA approval of a subcutaneous PD-1 inhibitor, setting a regulatory precedent for immune checkpoint inhibitors. The decision reflects the agency’s growing support for alternative administration routes that maintain efficacy while reducing treatment burden. Merck plans to submit additional global regulatory filings to health authorities in the European Union, Japan, and other major markets in 2025.
Business Significance
Advertisement
KEYTRUDA is Merck’s top-selling product, generating over $25 billion in annual revenue. The approval of the QLEX subcutaneous formulation provides a strategic opportunity to defend market share as competition from next-generation checkpoint inhibitors intensifies. By offering both IV and SC dosing, Merck can meet diverse patient and clinic preferences, strengthen hospital contracts, and extend patent protection through the new formulation. Analysts project that subcutaneous delivery could shift a meaningful percentage of U.S. and global KEYTRUDA usage to the QLEX format, supporting continued revenue growth beyond the expected expiration of core patents later this decade.
Patients’ Significance
For patients, the ability to receive pembrolizumab via a short subcutaneous injection instead of a 30-minute intravenous infusion offers substantial improvements in convenience and quality of life. This option reduces time spent in infusion centers, lowers the need for intravenous access, and may ease the burden on caregivers. Subcutaneous administration is particularly beneficial for patients with difficult venous access or those receiving combination therapies that already require lengthy infusion times. Importantly, the KEYNOTE-D77 trial confirmed that efficacy and safety remain consistent between SC and IV dosing, ensuring that patients receive the same life-prolonging benefits.
Policy Significance
The introduction of subcutaneous checkpoint inhibitor therapy aligns with healthcare policy trends focused on value-based care and treatment efficiency. SC administration can reduce infusion chair time, improve clinic throughput, and lower indirect costs associated with cancer treatment, such as transportation and lost work hours. Payers may also benefit from reduced administration costs compared to IV infusion, particularly as biosimilar competition drives pricing pressure. The FDA’s decision reinforces the importance of regulatory flexibility in adopting novel delivery methods that enhance patient access and system sustainability without compromising clinical outcomes.
Transaction Highlights
The FDA approval of KEYTRUDA QLEX is the result of a multi-year development program and a strategic collaboration between Merck and Halozyme Therapeutics, leveraging Halozyme’s proprietary ENHANZE® drug-delivery technology to enable high-volume subcutaneous administration of pembrolizumab. Merck conducted the pivotal Phase 3 KEYNOTE-D77 trial, which demonstrated that the subcutaneous formulation achieved pharmacokinetic equivalence, comparable efficacy, and a consistent safety profile versus the standard intravenous formulation across a broad range of solid tumor indications. Merck holds global commercialization rights to KEYTRUDA QLEX and plans an immediate U.S. launch, followed by submissions to the European Medicines Agency (EMA), Japan’s Pharmaceuticals and Medical Devices Agency (PMDA), and other regulatory authorities worldwide. This approval highlights Merck’s lifecycle management strategy to extend the commercial and clinical reach of KEYTRUDA through innovative delivery formats, while strengthening its competitive position in the rapidly evolving immuno-oncology market.
Source: Merck & Co., Inc. Press Release
