Antibody-drug conjugates (ADCs) are being studied in various diseases, including cancer, autoimmune and infectious diseases. In cancer, ADCs are made up of a monoclonal antibody that binds to specific proteins on cancer cells, and a chemotherapy drug attached to the antibody by a linker. ADC cancer therapies deliver a powerful dose of chemotherapy to specific cancerous cells, damaging the intruders without harming healthy cells elsewhere in the body, and are generally used when cancers recur, spread, or exhibit treatment resistance.
This summer, three pharma giants — Merck & Co., Gilead Sciences, and AstraZeneca — have all been competing to advance the next generation of ADC cancer therapies, running a total of 33 ADC-related Phase 3 clinical trials across companies. Merck initiated the latest trial, registering a trial coded TroFuse-020 on June 14, 2024. It marked Merck’s tenth global phase 3 trial for an ADC called sacituzumab tirumotecan, also known as sac-TMT, per Fierce Pharma. Read on to find out more about the race for effective ADC cancer therapies in the ultra-competitive pharma field.
Pharma Giants Race to Improve ADC Cancer Therapies
As of January 2024, there were 12 FDA-approved ADCs available to cancer patients and their providers. Merck, Gilead Sciences, and AstraZeneca are now all working to launch a specific type of ADC: one that targets trophoblast cell-surface antigen 2 (TROP2), a common protein that’s overexpressed in many tumors. Gilead officially released Trodelvy, the first TROP2-directed ADC, in 2020. Now, many industry experts predict that AstraZeneca will be next, with a drug known as datopotamab deruxtecan, or Dato-DXd. Each of these drugs has extensive Phase 3 programs that are either currently planned, underway, or completed. Each trial was designed with early-stage triple-negative breast cancer (TNBC) patients in mind, targeting one of the most aggressive types of breast cancer.
Why are the companies moving so fast? Fierce Pharma reports that the three ADCs currently undergoing testing have a unique quality: They each use topoisomerase I inhibitors as their “cancer-killing payloads,” and this inhibitor creates secondary resistance to future payloads. Essentially, the drugs can’t be used after one another. This could dramatically reduce each company’s access to patients in the future, hence the rush.
Can ADC Cancer Therapies Advance Beyond Phase 3?
To progress beyond the current phase of clinical trials, the three TROP2 ADCs must clear several hurdles. First, the manufacturers must address several undeniable safety concerns, including diarrhea and stomatitis, a painful inflammation of the mouth. To ensure a successful therapy, these drug companies must address patients’ exposure to toxicity, as well as their overall quality of life. Moving forward, if any of the companies clear Phase 3, they will be able to request FDA approval to market their ADC cancer therapies in a process known as New Drug Approval (NDA). This would mark a major step in treating aggressive, treatment-resistant cancers.
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Merck & Co., Gilead Sciences, and AstraZeneca are all racing toward improved ADC cancer therapies to remain competitive in the complex world of cancer treatment possibilities; however, the bottom line is far from the only consideration for the drug companies. The faster an ADC receives FDA approval, the faster patients will be able to benefit from these new powerful, highly targeted therapies.
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