Researchers at The University of Texas MD Anderson Cancer Center have found that a combination of two investigational drugs, zedoresertib and lunresertib, shows significant promise in treating advanced ovarian cancer in patients with certain genetic alterations. In early clinical trials, the combination achieved a 60% overall response rate in patients with CCNE1 amplification, a genetic change that makes tumors particularly difficult to treat. The FDA has granted the combination Fast Track Designation, a pathway that accelerates development of drugs addressing serious conditions with unmet medical needs .

What Are These Drugs and How Do They Work?

Zedoresertib and lunresertib represent a new approach to cancer treatment called synthetic lethality, which exploits specific genetic weaknesses in cancer cells. Zedoresertib is a WEE1 kinase inhibitor, meaning it blocks a protein that acts as a gatekeeper of the cell cycle. Cancer cells with DNA damage normally use this gatekeeper to buy time for repairs before dividing. By blocking WEE1, zedoresertib forces damaged cancer cells into division prematurely, causing them to die .

Lunresertib works through a complementary mechanism by inhibiting a protein called PKMYT1, which regulates the cell cycle through a different pathway. Together, the two drugs create a powerful one-two punch against tumors harboring specific genetic mutations. The combination was designed to work synergistically, meaning the drugs enhance each other's effectiveness .

What Did the Clinical Trial Show?

The Phase I MYTHIC trial enrolled 62 patients with advanced, treatment-resistant solid tumors that carried specific genetic alterations, including CCNE1 amplification or mutations in FBXW7 or PPP2R1A genes. Patients had various cancer types, including ovarian, colorectal, pancreatic, and breast cancers. Researchers tested different dosing schedules to determine the safest and most effective approach .

The results were encouraging across multiple measures. Among 54 evaluable patients across all dosing levels, 68.5% showed disease control, meaning their cancer either shrank or remained stable. In patients with target lesions that could be measured, 26 showed tumor shrinkage and 10 achieved a radiological response. The molecular response rate, which measures changes at the genetic level, was 47% across all patients and 67% in those with advanced ovarian cancer .

For ovarian cancer specifically, the results were particularly striking. Among patients with advanced ovarian cancers harboring the targeted genetic mutations, 80% showed consistent tumor shrinkage with durable responses. At least 10 patients remained on treatment for more than 16 weeks, and five patients continued treatment for longer than 32 weeks, suggesting the benefits were sustained over time .

How Did Patients Tolerate the Treatment?

Safety is always a critical consideration in cancer treatment. The good news is that the combination was generally well-tolerated, with a manageable side effect profile consistent with what researchers expected from either drug used alone. The most commonly reported side effects were mild to moderate, including nausea, vomiting, and asthenia, a medical term for generalized fatigue or weakness .

Steps to Understanding Your Cancer Treatment Options

• Genetic Testing: If you have been diagnosed with ovarian cancer or another solid tumor, ask your oncologist whether genetic testing for CCNE1 amplification or FBXW7 and PPP2R1A mutations might be appropriate for your case, as these tests can identify whether you might benefit from targeted therapies.
• Clinical Trial Eligibility: Discuss with your healthcare team whether you might qualify for clinical trials testing new drug combinations, particularly if standard treatments have not been effective or are no longer working.
• FDA Fast Track Designation: Learn what Fast Track Designation means for a drug in development; it indicates the FDA believes the therapy addresses a serious condition with significant unmet medical need and may reach patients faster than standard approval timelines.

The significance of this research lies in addressing a critical gap in cancer treatment. Ovarian cancer, particularly in patients with CCNE1 amplification, has historically been difficult to treat effectively. Many patients develop resistance to standard chemotherapy, leaving them with limited options. This new combination offers a potential breakthrough for this vulnerable population .

"This combination demonstrated strong synergy in preclinical studies, and we have now demonstrated its great potential as a novel therapeutic option for patients across multiple tumor types, especially for those with ovarian cancer," stated Timothy Yap, professor of Investigational Cancer Therapeutics and vice president and head of clinical development in UT MD Anderson's Therapeutics Discovery division.

Timothy Yap, M.B.B.S., Ph.D., Professor of Investigational Cancer Therapeutics at The University of Texas MD Anderson Cancer Center

Yap added that patients with cancers harboring these specific genetic alterations represent an area of significant unmet clinical need, and this combination could provide a new treatment option where few currently exist .

What Happens Next?

The MYTHIC trial is ongoing, and researchers continue to optimize the dosing and scheduling of this combination across the various tumor types represented in the study. The FDA Fast Track Designation means the drug developers and the agency will work together more closely to expedite the development process. This could potentially bring the treatment to patients faster than the standard approval timeline, though additional trials will still be necessary to confirm the benefits and establish the optimal patient population .

For patients with advanced ovarian cancer or other solid tumors with these genetic alterations, this research represents a meaningful step forward. While the trial is still in its early phases, the combination of strong response rates, durable benefits, and manageable side effects suggests this approach warrants continued investigation and development.