FDA Approves Application for ABT-301 in Metastatic Colorectal Cancer

The U.S. Food and Drug Administration (FDA) has approved an investigational new drug application for ABT-301, clearing the way for the initiation of a phase 1/2 clinical trial of the drug in combination with Tevimbra (tislelizumab) and Avastin (bevacizumab) for the treatment of patients with metastatic colorectal cancer. 

The development was announced in a news release issued by Anbogen Therapeutics, the clinical-stage biotechnology company behind ABT-301.

The upcoming open-label, multi-center international study aims to enroll approximately 66 patients with proficient mismatch repair or non-microsatellite instability-high metastatic colorectal cancer, with patient enrollment planned in Taiwan and Australia.

ABT-301, according to Anbogen Therapeutics, is a HDAC1/2/3 inhibitor with immune-modulating capabilities which enhances the tumor microenvironment and boosts immune responses. This mechanism of action is intended to improve the effectiveness of immune checkpoint inhibitors in the treatment of metastatic colorectal cancer.

Tevimbra, as defined by the National Cancer Institute, is a type of monoclonal antibody and immune checkpoint inhibitor that binds to the protein PD-L1 in order to help immune cells better kill cancer cells. Avastin, according to the National Cancer Institute, binds to the protein VEGF, which may prevent the growth of new blood vessels that tumors need to grow and is a type of antiangiogenesis agent and a monoclonal antibody.

Anbogen Therapeutics further noted in the news release that in a prior phase 1 clinical trial, ABT-301 did not result in neutropenia or cardiac toxicity, both of which are found to be commonly observed with other inhibitors similar to ABT-301.

In results from the first-in-human trial of ABT-301, presented at the American Society of Clinical Oncology Annual Meeting in 2023 and published in the Journal of Clinical Oncology, researchers noted that “ABT-301 was well-tolerated at a daily dose of up to 150 [milligrams] and demonstrated objective responses and long-term [stable disease] across multiple tumor types at [the maximum tolerated dose]. The safety profile of ABT-301 was superior to known HDAC inhibitors with only predictable HDAC inhibitor-related toxicities observed but no cardiac toxicity, neutropenia nor lymphopenia elicited. Non-clinical and clinical results suggested the potential clinical development of ABT-301 in combination with myelosuppressive agents and immunotherapies.”

According to Anbogen Therapeutics, approximately 95% of patients with metastatic colorectal cancer are proficient mismatch repair or non-microsatellite instability-high subtypes, which are referred to as “cold tumors” and typically respond poorly to current immunotherapy offerings.

Colorectal cancer, as explained by the American Cancer Society, starts in the colon or in the rectum. These cancers can also be referred to as colon cancer or rectal cancer, depending on their point of origin, and are often grouped together because of the many features they have in common.

Colorectal cancer is, excluding skin cancers, the third most-common cancer that is diagnosed in both men and women in the United States, the American Cancer Society states, estimating that in 2025 there will be approximately 107,320 new cases of colon cancer and approximately 46,950 new cases of rectal cancer in the United States. Furthermore, they stated men have a 1 in 24 risk and women have a 1 in 26 risk of developing colorectal cancer in their lifetimes.

Additionally, in the United States colorectal cancer is the third-leading cause of cancer-related deaths in men and the fourth leading cause of cancer-related deaths in women, but is the second most-common cause of cancer death when the numbers are combined, and is expected to result in approximately 52,900 deaths this year, according to the American Cancer Society.

For more news on cancer updates, research and education, don’t forget to subscribe to CURE®’s newsletters here.

References

1. “Anbogen Receives FDA Clearance to Initiate Phase 1/2 Trial of ABT-301 Triplet Therapy for Advanced Colorectal Cancer,” by Anbogen Therapeutics. News Release. Augst 4, 2025.
2. "Tevimbra," by the National Cancer Institute. https://www.cancer.gov/publications/dictionaries/cancer-terms/def/tevimbra.
3. "Avastin," by the National Cancer Institute. https://www.cancer.gov/publications/dictionaries/cancer-terms/def/avastin.
4. "Phase I first-in-human trial of ABT-301, an oral pan-HDAC inhibitor, in patients with advanced solid tumors," by Dr. Chia-Chi Lin, et al. Journal of Clinical Oncology.