Can Merck’s new Keytruda injection delay biosimilar threats and change cancer care forever?

What makes the FDA approval of Merck’s Keytruda QLEX a turning point in cancer immunotherapy delivery?

Merck & Co. (NYSE: MRK) has received U.S. Food and Drug Administration (FDA) approval for Keytruda QLEX—a fixed-dose subcutaneous formulation of pembrolizumab combined with berahyaluronidase alfa—for use in adult and adolescent patients across nearly all solid tumor indications currently covered by intravenous Keytruda.

This injectable version, which can be administered in just one minute every three weeks or two minutes every six weeks, represents a major evolution in how checkpoint inhibitors are delivered. The product is expected to become available in the U.S. by late September 2025 and is seen as a critical part of Merck’s lifecycle strategy for Keytruda, its top-selling immuno-oncology therapy.

How does Keytruda QLEX compare with intravenous Keytruda in terms of clinical efficacy and safety?

The FDA’s decision was based on data from Study MK-3475A-D77, a multicenter Phase 3 trial conducted in 377 patients with treatment-naïve metastatic non-small cell lung cancer (NSCLC). Participants received either Keytruda QLEX (790 mg/9,600 units) or intravenous pembrolizumab (400 mg) in combination with chemotherapy every six weeks.

The subcutaneous formulation met the trial’s primary pharmacokinetic endpoint by demonstrating comparable drug exposure levels at Cycle 1 AUC0–6 weeks and Cycle 3 Ctrough. The confirmed overall response rate (ORR) for Keytruda QLEX was 45% (95% CI: 39–52), slightly higher than the 42% (95% CI: 33–51) seen with IV Keytruda. No significant differences were observed in progression-free survival (PFS) or overall survival (OS).

Safety profiles were also aligned. The most common adverse events in the QLEX arm included nausea (25%), fatigue (25%), and musculoskeletal pain (21%).

Why are oncologists and institutional investors watching the Keytruda QLEX rollout closely?

Keytruda QLEX may streamline clinical workflows, ease pressure on infusion centers, and improve the patient experience, particularly for those with difficult venous access. Subcutaneous administration requires far less time than the 30-minute IV infusions and allows administration at alternative sites such as local outpatient clinics or community-based oncology centers.

Institutional investors and analysts view this approval as a strategic buffer against the upcoming Keytruda patent cliff in 2028. Biosimilar competition is inevitable, and QLEX’s differentiation through convenience and administration flexibility could preserve market share and delay the erosion of Merck’s oncology revenues. Some analysts estimate that 30–40% of current Keytruda users could transition to the QLEX formulation by 2027.

What are the potential challenges in market uptake of Keytruda QLEX despite FDA approval?

Despite the regulatory greenlight, Merck must navigate payer acceptance, clinic readiness, and reimbursement parity between IV and SC versions. Some insurance providers may require updated guidelines or formularies before covering the subcutaneous formulation. Additionally, oncologists will need to weigh cost dynamics and operational reconfigurations associated with switching delivery modes.

Moreover, while the approval covers 38 Keytruda indications, the clinical evidence underpinning QLEX is currently strongest in NSCLC. Wider real-world data will be necessary to validate comparable outcomes across diverse tumor types such as melanoma, cervical cancer, renal cell carcinoma, triple-negative breast cancer, and hepatocellular carcinoma.

How does Merck’s strategic positioning with Keytruda QLEX affect its broader oncology portfolio?

With over $25 billion in global sales in 2024, Keytruda remains Merck’s flagship oncology product. By rolling out QLEX now, the American drugmaker is aiming to establish a differentiated, patent-protected revenue stream that could extend the commercial longevity of the Keytruda franchise even as biosimilars prepare to enter the market post-2028.

Merck’s oncology leadership, including Dr. Marjorie Green, highlighted QLEX as part of a patient-centric vision for the future of cancer care—offering flexibility without compromising efficacy. Industry stakeholders, including Cancer Support Community CEO Sally Werner, also acknowledged the potential for QLEX to improve access, especially in underserved communities.

What does the subcutaneous checkpoint inhibitor landscape look like following this milestone?

Keytruda QLEX is the first and only approved subcutaneous PD-1 inhibitor in the U.S., giving Merck a significant first-mover advantage. Rivals such as Bristol Myers Squibb and Roche are also pursuing subcutaneous versions of nivolumab and atezolizumab respectively, but Merck’s approval may set a new clinical and commercial benchmark.

The collaboration with Alteogen Inc., the developer of the hyaluronidase enzyme used in QLEX, also underscores a trend where biopharma players are leveraging bio-enhancer technologies to reformulate blockbuster therapies for easier administration and longer product lifecycle protection.

What’s next for Merck’s global expansion and lifecycle strategy for Keytruda QLEX?

European and Asian regulatory filings for Keytruda QLEX are expected to follow soon, with potential decisions from the European Medicines Agency (EMA) anticipated in early 2026. In parallel, Merck is likely to invest in provider education, payer negotiations, and potentially real-world evidence programs to support adoption across multiple oncology settings.

With KEYTRUDA QLEX positioned as a new injectable platform, Merck is also evaluating its use in additional combination regimens and earlier lines of therapy, especially in neoadjuvant and adjuvant settings. As treatment paradigms evolve toward convenience, speed, and accessibility, QLEX may play a defining role in reshaping delivery models for immuno-oncology drugs.

How does the launch of Keytruda QLEX fit into Merck’s broader pipeline and lifecycle strategy?

The approval of Keytruda QLEX is not just about convenience—it’s a key move in Merck’s broader oncology strategy. As of 2025, Keytruda remains a cornerstone of the company’s immuno-oncology revenue, accounting for over 40% of pharmaceutical sales. With the patent for intravenous Keytruda set to expire in the U.S. in 2028, Merck is racing to extend the commercial life of the molecule through novel formulations, indication expansions, and combination regimens.

The QLEX format gives Merck a new IP-protectable product, potentially allowing the firm to segment markets and pricing tiers across payer geographies. According to institutional analysts, this opens up layered strategies—one where QLEX could be offered at a premium in outpatient oncology settings, while biosimilar IV versions will be relegated to hospital procurement chains. This dual-channel approach could help Merck retain formulary control even after patent expiration.

What does this approval mean for real-world patient access and oncology workforce planning?

For patients, especially those in rural or resource-constrained settings, subcutaneous administration offers a critical upgrade. Rather than relying on infusion center capacity and availability, patients could theoretically receive treatment at local health clinics or ambulatory care units. This decentralization of administration has the potential to reduce wait times and improve treatment adherence—key goals in oncology outcomes optimization.

Clinicians, too, are likely to welcome QLEX for its workflow efficiency. Infusion chairs, typically occupied for over 30 minutes per Keytruda session, can now be freed up within minutes. For high-volume oncology centers managing multiple infusion regimens, this can significantly increase patient throughput and reduce the cost-per-treatment minute. It may also ease staffing constraints, allowing nurse practitioners to deliver immunotherapy in broader settings without full IV infusion certification requirements.

How are competitors responding to Merck’s first-mover advantage with subcutaneous checkpoint inhibitors?

The approval of Keytruda QLEX sets a precedent in a therapeutic category that has traditionally relied on intravenous access. Other pharmaceutical companies with PD-1/PD-L1 inhibitors in their portfolio—such as Bristol Myers Squibb (nivolumab/Opdivo), Roche (atezolizumab/Tecentriq), and AstraZeneca (durvalumab/Imfinzi)—are reportedly working on similar subcutaneous formulations, but none have reached commercial approval in the U.S. yet.

In Europe, Roche is further along, with its SC version of Tecentriq already approved in select indications. However, Merck’s broader FDA approval across nearly all solid tumor indications gives it a defensible moat, at least temporarily. That said, as subcutaneous versions become the norm, payer pressure may force competition not just on efficacy and safety—but on time-to-administer, convenience, and delivery economics.

What role does Alteogen play in the development of Keytruda QLEX—and could it impact formulation tech partnerships?

The technology enabling QLEX’s subcutaneous absorption hinges on berahyaluronidase alfa, an engineered enzyme variant developed by Alteogen Inc.. The South Korean biotech licensed the recombinant hyaluronidase technology to Merck, enabling enhanced tissue permeability for large monoclonal antibodies like pembrolizumab.

This collaboration reflects a growing trend in pharma where biotech formulation enablers—often small or mid-cap firms—are critical to extending the utility of blockbuster molecules. The QLEX success may drive more deals of this nature, where biopharma giants co-develop delivery platforms to overcome patent cliffs and reposition existing therapies in competitive markets.

How does the safety profile of Keytruda QLEX compare across specific adverse event categories?

In addition to efficacy and pharmacokinetics, the safety profile of Keytruda QLEX is under particular scrutiny. The FDA’s prescribing information highlights potential risks of immune-mediated adverse events, consistent with the mechanism of PD-1 blockade. These include pneumonitis (5% incidence), colitis (1.2%), thyroid disorders (22–33% combined for hypo- and hyperthyroidism), and dermatologic reactions (1.6%).

The safety data remain largely comparable with those of IV Keytruda, with no new signals emerging in the QLEX formulation. However, clinicians are advised to closely monitor for signs of immunotoxicity and administer systemic corticosteroids or withhold therapy based on severity, as outlined in the product labeling.