Ovarian cancer has long been one of the most challenging cancers to treat, especially platinum‑resistant forms where standard chemotherapy fails early. In February 2026, the U.S. Food and Drug Administration (FDA) granted a landmark approval that could transform outcomes for many patients: Keytruda (pembrolizumab) and its subcutaneous variant Keytruda Qlex (pembrolizumab and berahyaluronidase alfa‑pmph), in combination with paclitaxel (with or without bevacizumab), have been approved for adults with PD‑L1 positive platinum‑resistant epithelial ovarian, fallopian tube, or primary peritoneal carcinoma after one or two prior systemic treatments.
This blog unpacks:
Ovarian cancer typically begins in the ovaries or fallopian tubes and is often treated initially with surgery and platinum‑based chemotherapy. For many patients, these interventions are effective at first. However, platinum resistance develops when the cancer progresses within six months of platinum therapy, meaning standard chemotherapy no longer controls the disease.
Traditional chemotherapy regimens may stabilize disease temporarily, but survival gains have historically been modest. For decades clinicians and researchers sought therapies that could deliver better progression‑free survival (PFS) and overall survival (OS) for this population.
Keytruda is the trade name for pembrolizumab, a type of immune checkpoint inhibitor. It works by blocking the PD‑1 receptor on immune cells, releasing brakes on the immune system so it can recognize and attack cancer cells more effectively. By targeting the PD‑1/PD‑L1 pathway, Keytruda helps the body overcome one of the mechanisms tumors use to hide from immune attack.
Keytruda Qlex is a newer formulation that combines pembrolizumab with berahyaluronidase alfa, an enzyme that enhances drug dispersion when given via subcutaneous injection (under the skin) instead of intravenous infusion. This can provide a more convenient administration option with equivalent therapeutic effect.
These therapies are already approved for multiple cancer types, such as melanoma, lung cancer, and certain gastric cancers, and now join the ovarian cancer landscape thanks to recent trial data.
The FDA decision was grounded in results from the Phase 3 KEYNOTE‑B96 trial (also known as ENGOT‑ov65), a pivotal study designed to evaluate the addition of pembrolizumab to paclitaxel chemotherapy in patients with platinum‑resistant ovarian cancer whose tumors express PD‑L1 (combined positive score [CPS] ≥1).
These improvements were statistically significant and clinically meaningful for a population with otherwise limited options.
Not all ovarian cancers are the same. A key biomarker in this approval is PD‑L1 expression, measured by the combined positive score (CPS). PD‑L1 is a protein expressed by tumor and immune cells that interacts with the PD‑1 receptor to dampen immune responses. Tumors with higher PD‑L1 expression are more likely to respond to PD‑1 inhibitors like Keytruda.
This approval specifically applies to patients with CPS ≥1, indicating that tumor tissue shows enough PD‑L1 expression to justify treatment with immune checkpoint therapy. Companion diagnostic tools like the PD‑L1 IHC 22C3 pharmDx assay were also cleared to help clinicians determine eligibility.
This approval matters for several reasons:
Keytruda and Keytruda Qlex now represent the first and only PD‑1 inhibitors approved for platinum‑resistant ovarian cancer with PD‑L1 expression. Previously, immunotherapy’s role in ovarian cancer was unclear, with past studies showing limited activity in unselected populations. This regulatory milestone changes that narrative.
Many patients relapse after first‑line platinum chemotherapy. Once platinum resistance develops, options are sparse and often palliative. Adding an immunotherapy regimen provides new hope for delaying progression and potentially extending life.
The approval underscores the value of biomarker‑driven therapy. Testing for PD‑L1 now has direct therapeutic implications in ovarian cancer, aligning treatment more closely with individual tumor biology.
With any cancer therapy, particularly immunotherapies, benefits must be balanced against risks. Keytruda and Keytruda Qlex have well‑characterized safety profiles from both the KEYNOTE‑B96 trial and prior studies in other cancers.
These include immune‑related effects that can impact various organ systems:
In KEYNOTE‑B96 specifically, common reactions included diarrhea (45%), fatigue (43%), nausea (41%), alopecia (38%), and lab abnormalities like anemia and leukopenia.
Immune checkpoint blockade can cause serious immune‑mediated reactions affecting lungs (pneumonitis), colon (colitis), liver (hepatitis), endocrine glands, and kidneys. Prompt recognition and management are critical. These events can be severe or even fatal if unrecognized.
Clinicians must monitor patients closely and educate them on symptoms that warrant immediate medical attention.
Leading oncologists hail this decision as a game‑changer:
“For many patients with ovarian cancer, the disease can become platinum‑resistant. At that point options are limited and the reality can change very quickly. These approvals offer the possibility of more time.” – Gynecologic Oncologist
This reflects a broader confidence within the oncology community that immunotherapy can deliver durable benefits outside traditionally responsive cancers like melanoma and lung cancer.
Patients eligible for this therapy should:
This approval does not mean Keytruda will work for everyone—but for patients with PD‑L1 positive platinum‑resistant disease, it represents a meaningful new treatment avenue.
The KEYNOTE‑B96 results not only secured approval but also open doors to further research:
Immunotherapy’s footprint in ovarian cancer is growing, reversing decades of stagnation in late‑stage treatment innovation.
The FDA’s approval of Keytruda and Keytruda Qlex, in combination with chemotherapy with or without bevacizumab, is a significant advance in the treatment of PD‑L1 positive platinum‑resistant ovarian cancer. Backed by robust clinical data from the KEYNOTE‑B96 trial, this development gives patients and clinicians a new and powerful tool in a previously hard‑to‑treat setting. As personalized oncology continues to evolve, this approval highlights the importance of biomarkers and immune‑based therapies in transforming patient outcomes.
This article is for educational and informational purposes only and does not replace professional medical advice. Treatments must be discussed with qualified healthcare professionals, considering individual clinical factors. Always consult your clinician before starting or changing cancer therapies.
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