The European Commission (EC) has granted approval for Keytruda (pembrolizumab) in combination with paclitaxel, with or without bevacizumab, as a vital new treatment option for adults with programmed death-ligand 1 (PD-L1)-positive platinum-resistant ovarian cancer. This significant regulatory milestone, announced by Merck (known as MSD outside the US and Canada), marks a crucial advancement in the therapeutic landscape for a challenging and often life-limiting form of gynecological malignancy. The approval extends to Keytruda SC, which is recognized in the United States as Keytruda Qlex, a formulation incorporating pembrolizumab and berahyaluronidase alfa-pmph, designed for subcutaneous administration.
Expanding Treatment Horizons for Relapsed Ovarian Cancer
The European Union’s endorsement specifically targets adult patients diagnosed with platinum-resistant epithelial ovarian, fallopian tube, or primary peritoneal carcinoma. A critical criterion for eligibility is the presence of PD-L1 expression in their tumors, quantified by a combined positive score (CPS) of one or more. Furthermore, these patients must have previously received one or two systemic treatment regimens, indicating a need for more effective subsequent therapeutic strategies. This approval underscores the growing importance of immunotherapy in tackling advanced and recurrent cancers, offering a new avenue for patients whose disease has progressed despite initial treatments.
The decision from the European Commission follows a favorable opinion issued in February 2026 by the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMA). This recommendation from the CHMP, a key advisory body to the EC, is typically based on a thorough review of extensive clinical trial data and signifies a strong consensus among regulatory experts regarding the drug’s safety and efficacy.
Foundation in Landmark Clinical Trial Data
The cornerstone of this regulatory approval is the robust data generated from the Phase III KEYNOTE-B96 trial, also referred to as ENGOT-ov65. This pivotal international study was designed to rigorously evaluate the efficacy and safety of Keytruda in combination with chemotherapy for patients with advanced, platinum-resistant ovarian cancer.
The KEYNOTE-B96 trial demonstrated a statistically significant and clinically meaningful improvement in progression-free survival (PFS) – the primary endpoint of the study – for patients treated with Keytruda plus paclitaxel, with or without bevacizumab, compared to those who received a placebo in conjunction with paclitaxel, with or without bevacizumab. Progression-free survival is a critical measure in cancer treatment, indicating the duration for which a patient lives without their cancer worsening. A significant improvement in PFS suggests that the new treatment regimen can effectively control tumor growth for a longer period.
Beyond PFS, the trial also reported a favorable impact on overall survival (OS), a key secondary endpoint. Overall survival represents the length of time patients are alive following a diagnosis or the start of treatment. The observed improvement in OS further solidifies the clinical benefit of the Keytruda-based regimen for this patient population. The study specifically focused on patients whose tumors exhibited PD-L1 expression with a Combined Positive Score (CPS) of at least one, highlighting the predictive value of this biomarker in identifying individuals most likely to benefit from immunotherapy.
A New Era for Ovarian Cancer Treatment in Europe
Dr. Gursel Aktan, Vice President of Global Clinical Development at Merck Research Laboratories, expressed optimism about the approval’s implications. "We’re proud to bring this Keytruda-based regimen to appropriate patients in Europe with PD-L1-positive platinum-resistant ovarian cancer – giving this community access to the region’s first PD-1 inhibitor treatment approach for this disease," Dr. Aktan stated. He further emphasized, "This milestone marks real progress for patients and advances our broader mission of expanding access to effective options for women’s cancers globally."
The inclusion of PD-1 inhibitor therapy as a first-in-class option for this specific patient group represents a paradigm shift. Historically, treatment options for platinum-resistant ovarian cancer have been limited, often involving sequential chemotherapy regimens with diminishing efficacy and significant side effects. The introduction of an immunotherapy agent like Keytruda, which works by harnessing the patient’s own immune system to fight cancer, offers a fundamentally different approach with the potential for more durable responses and improved quality of life.
Geographic Reach and Regulatory Alignment
The European Commission’s approval is comprehensive, encompassing all 27 EU member states. Additionally, the authorization extends to Norway, Iceland, and Liechtenstein, ensuring broad access to this new therapeutic option across a significant portion of Europe.
This European endorsement aligns with regulatory decisions made in other major markets. Notably, in February 2026, the U.S. Food and Drug Administration (FDA) approved the identical Keytruda combination regimen for the same adult patient population. This parallel approval by two of the world’s leading regulatory bodies underscores the global consensus on the clinical utility and benefit of this treatment strategy.
Understanding Ovarian Cancer and the Role of PD-L1
Ovarian cancer is a complex disease characterized by its often late diagnosis and resistance to conventional therapies. It is the eighth most common cancer in women worldwide, and unfortunately, one of the deadliest due to its tendency to spread silently in the early stages. Platinum-based chemotherapy is a cornerstone of treatment for most ovarian cancers, but many patients eventually develop resistance, meaning their cancer stops responding to these drugs. Platinum-resistant ovarian cancer is defined by progression of the disease within six months of completing platinum-based chemotherapy.
The development of resistance is a significant challenge, and the identification of biomarkers that can predict treatment response is crucial for personalized medicine. Programmed death-ligand 1 (PD-L1) is a protein that can be expressed on cancer cells and immune cells. When PD-L1 binds to its receptor, PD-1, found on T-cells (a type of immune cell), it can suppress the immune response, allowing cancer cells to evade detection and destruction by the immune system. By blocking the interaction between PD-L1 and PD-1, Keytruda, a PD-1 inhibitor, can "release the brakes" on the immune system, enabling T-cells to effectively attack and eliminate cancer cells. The requirement for PD-L1 positivity (measured by CPS ≥ 1) in the approved indication reflects the scientific understanding that patients whose tumors express PD-L1 are more likely to benefit from PD-1 inhibitor therapy.
The Significance of Keytruda SC (Keytruda Qlex)
The approval of Keytruda SC (pembrolizumab and berahyaluronidase alfa-pmph) in the European Union, known as Keytruda Qlex in the US, represents an important advancement in patient convenience and treatment administration. This formulation is designed for subcutaneous injection, which can be administered by a healthcare professional under the skin, as opposed to intravenous infusion, which requires a vein and typically takes longer. Subcutaneous administration can lead to shorter infusion times, potentially reducing the burden on patients and healthcare systems, and may offer greater flexibility in treatment settings. This development reflects the ongoing innovation in drug delivery systems aimed at improving patient experience and adherence to therapy.
Future Implications and Ongoing Research
The EC’s approval of Keytruda in combination with chemotherapy for PD-L1-positive platinum-resistant ovarian cancer is a significant step forward, offering a much-needed new therapeutic option. However, the fight against ovarian cancer is ongoing, and research continues to explore the full potential of immunotherapies and novel treatment combinations.
Future research will likely focus on:
- Identifying broader patient populations: Investigating whether Keytruda or similar immunotherapies can benefit patients with lower levels of PD-L1 expression or those with different subtypes of ovarian cancer.
- Optimizing treatment sequencing: Determining the best placement of immunotherapy within the overall treatment journey for ovarian cancer, including its use in earlier lines of therapy or in combination with other novel agents.
- Predictive biomarkers: Developing more sophisticated biomarkers to accurately predict which patients will achieve the greatest benefit from immunotherapy, thereby personalizing treatment decisions and minimizing exposure to ineffective therapies.
- Managing and overcoming resistance: Understanding the mechanisms by which ovarian cancer can develop resistance to immunotherapy and developing strategies to overcome or prevent this resistance.
The journey of Keytruda in ovarian cancer, from clinical trials to regulatory approvals, highlights the transformative power of targeted therapies and the importance of international collaboration in drug development and evaluation. This latest approval in Europe signifies a renewed sense of hope for patients facing this challenging diagnosis and underscores Merck’s commitment to advancing cancer care globally. The availability of both intravenous and subcutaneous formulations further enhances the accessibility and patient-centricity of this innovative treatment.
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