The healthcare and medical research sector has seen a prominent development after global pharmaceutical company GSK revealed early and promising clinical trial results for its new investigational drug. Scientifically known as ‘Miratertuzumab soventecan’ and referred to as ‘Mireiz’ for short, it belongs to the class of antibody-drug conjugates. Recent data showed that this innovative treatment successfully shrank malignant tumors in the majority of patients suffering from refractory gynecological cancers that are difficult to treat with conventional methods.
This important data was presented on Sunday at the Society of Gynecologic Oncology’s 2026 Annual Meeting on Women’s Cancer, held in San Juan, Puerto Rico. These positive results have established a solid foundation for the company’s ambitious plans to launch 5 pivotal late-stage trials during the current year.
Significant tumor shrinkage in early stages
Platinum-resistant ovarian cancer and advanced endometrial cancer are among the most complex medical challenges in the field of gynecological oncology. Often, patients’ response to standard chemotherapies wanes, leading to disease progression and spread. This is where modern drugs highlight their importance, offering a new glimmer of hope for this group of patients who have exhausted available treatment options.
In the details of the results, the phase 1 trial named ‘BeHOLD-1’ demonstrated confirmed objective response rates of 62 percent in 34 patients with platinum-resistant ovarian cancer when using the maximum dose of 5.8 milligrams per kilogram of body weight. In another cohort, the response rate reached 67 percent in 12 patients with recurrent or advanced endometrial cancer receiving a dose of 4.8 milligrams per kilogram.
Adding to the significance of these findings, more than half of the patients participating in the study had previously undergone two or more lines of therapy. This patient group typically faces low survival chances, with 5-year survival rates ranging between only 20 to 30 percent, making any therapeutic progress at this stage a genuine medical achievement.
“Seeing this type of clinical activity and these response rates, which have been medically confirmed, is extremely exciting” – Hesham Abdullah
In this context, Hesham Abdullah, head of oncology research and development at GSK, told reporters ahead of the presentation, expressing great optimism. He added that the median follow-up period reached 6 months for the ovarian cancer group and 4 months for the endometrial cancer patients, confirming that treatment responses “continue to be durable.”
A safety profile supporting transition to phase III
Scientifically, the drug acts as an antibody-drug conjugate targeting the B7-H4 protein found on cancer cells. This technology delivers chemotherapy directly to infected cells, minimizing adverse impacts on surrounding healthy tissues. This explains the positive safety profile demonstrated by the drug during clinical trials.
Safety data provided highly encouraging indicators. For instance, interstitial lung disease, a type of toxicity associated with certain approved antibody-drug conjugates, appeared in only about 4 percent of patients in both cohorts. Furthermore, treatment-related adverse events led to discontinuation in only 2 percent of ovarian cancer patients and 4 percent of endometrial cancer patients. The most common side effect was neutropenia, a type of white blood cell responsible for fighting infection.
Expansion plans and future testing
Building on these encouraging data, the company plans to launch 5 global phase 3 trials in the coming months. This step will begin with trials focusing on platinum-resistant ovarian cancer and second-line endometrial cancer under the names ‘BeHOLD-Ovarian 01’ and ‘BeHOLD-Endometrial 01’. Additionally, further trials will evaluate the drug’s efficacy in treating platinum-sensitive ovarian cancer, frontline ovarian cancer, and first-line endometrial cancer.
It is worth noting that this investigational drug was acquired by GSK under a license from China’s Hansoh Pharma in October 2023. This license grants global rights to commercialize and develop the drug outside mainland China, Hong Kong, Macau, and Taiwan.
When asked whether he believes the drug has the potential to become a blockbuster medicine in global markets, Hesham Abdullah’s answer was decisive and clear, stating: “Do we think it will be a blockbuster? I would say, yes, absolutely.” This confidence reflects the widespread optimism within medical and pharmaceutical circles regarding the drug’s ability to revolutionize care for women with cancer.
Frequently Asked Questions
What is the investigational drug ‘Mireiz’?
It is a new investigational antibody-drug conjugate developed by GSK that targets cancer cells directly to shrink tumors while minimizing damage to healthy tissues.
What types of cancer does this drug treat?
The drug has shown significant efficacy in the early stages of treating refractory gynecological cancers, specifically platinum-resistant ovarian cancer and advanced or recurrent endometrial cancer.
When will phase 3 clinical trials for the drug begin?
GSK plans to launch 5 global phase 3 trials during 2026 to confirm the drug’s efficacy and safety ahead of official approval.
