[Edaily Reporter NA EUN-KYUNG ] “We are not trying to compete with existing immunotherapy drugs. APX-343A’s role is to make existing immunotherapy drugs more effective.”

As competition in the development of immuno-oncology drugs enters a period of stagnation, Aptabio Therapeutics Inc.(293780)is proposing a new approach with APX-343A. The strategy is not simply to create yet another immuno-oncology drug, but to develop APX-343A as a combination partner that increases the response rates of existing immuno-oncology drugs.

“Like Lenvima, which expanded Keytruda’s market”

Aptabio Therapeutics Inc. recently announced that in the Phase 1 clinical trial of its immuno-oncology candidate APX-343A, it achieved the same level of drug exposure (AUC) in humans as had been confirmed in animal studies. Following the first patient dosing in a combination trial with the blockbuster immunotherapy Keytruda on the 18th, the company plans to fully launch a Phase 1 clinical trial of the APX-343A+Keytruda combination with U.S.-based Merck (MSD) in the second half of the year, targeting patients with advanced solid tumors who have failed prior treatments.

Combination therapy is not a new concept in the anticancer drug market. Keytruda has also expanded its indications through various combination therapies. A prime example of this is the vascular endothelial growth factor (VEGF) inhibitor Lenvima.

Developed by Eisai, Lenvima (generic name: lenvatinib) has grown into a blockbuster drug by directly attacking cancer cells while simultaneously improving the tumor microenvironment (TME), thereby increasing Keytruda’s response rate. Currently, VEGF-targeted drugs are used in combination not only with Keytruda but also with numerous immuno-oncology agents, establishing themselves as major treatment options.

Aptabio Therapeutics Inc. believes that APX-343A has the potential to become the next-generation combination therapy to succeed Lenvima. The key difference is that APX-343A improves the tumor microenvironment by regulating cancer-associated fibroblasts (CAFs) rather than VEGF.

CEO Lee Soo-jin stated, “Most new drug candidates undergoing combination clinical trials with Keytruda were based on the concept of adding Mechanism A to Mechanism B. In contrast, APX-343A is a drug that, like Lenvima, creates an environment where immunotherapy can function properly.” She added, “Once proof of concept (PoC) is established in clinical trials, it could become an asset capable of being combined with various immunotherapies beyond Keytruda.”

For this reason, Aptabio Therapeutics Inc. believes that APX-343A is differentiated from many other candidates for combination with Keytruda. She emphasized, “One of the combination strategies that garnered the most attention for Keytruda was its use with VEGF inhibitors, ultimately because it enhanced Keytruda’s value as an immunotherapy in its own right.”

Therapeutic Concentrations Achieved in Humans… “Now Moving to the Efficacy Demonstration Phase”

Aptabio Therapeutics Inc. recently presented the results of a Phase 1 clinical trial of APX-343A as a monotherapy at ASCO 2026. According to the company, the drug achieved the same level of drug exposure (AUC) in humans as was observed in animal studies, and an increase in exposure was confirmed with increasing doses. No serious adverse events (SAEs) related to the drug or adverse effects of Grade 3 or higher were observed.

The CEO interpreted these data as signifying more than just confirmation of safety. He explained, “In new drug development, the likelihood of success increases when the exposure concentration that demonstrated efficacy in animal studies is achieved in humans as well,” adding, “Since we have confirmed that the drug is delivered properly in humans, we are now moving on to the stage of demonstrating anticancer efficacy in actual patients.”

The company has currently initiated a combination clinical trial with Keytruda and administered the first dose to a patient on the 18th. It is reviewing its development strategy with a focus on cancer types with high CAF expression, such as pancreatic cancer, triple-negative breast cancer, and cholangiocarcinoma, and aims to finalize the recommended combination dose (RP2D) by the end of the year.

CEO Lee said, “To date, there are virtually no CAF-modulating drugs that have advanced to the clinical stage,” adding, “We expect the CAF-modulating effects confirmed in animal studies to be demonstrated in clinical trials as well.”

The NOX Platform Expanding to Kidney and Eye Diseases

Aptabio Therapeutics Inc. views APX-343A not merely as an anticancer drug candidate, but as part of its NOX platform.

The NOX platform is a technology that regulates the pathways responsible for the production of reactive oxygen species that cause disease. Currently, the company is developing Isuzinacxib (APX-115), a treatment for diabetic nephropathy; APX-343A, an immuno-oncology drug; and ABF-101, an oral treatment for age-related macular degeneration—all based on this same platform.

CEO Lee cited scalability as the greatest strength of APX-343A. He explained that CAF is a pan-cancer biomarker not limited to specific cancer types, and once its mechanism of action is proven, its indications can be expanded to various types of cancer.

“If the concept that our drug enhances the efficacy of immunotherapy is proven in clinical trials, we can create continuous business development opportunities with multiple global pharmaceutical companies, rather than limiting ourselves to a technology export deal with a single company,” he said. “Our goal is to grow this into a platform that can once again transform the immunotherapy market.”

Since Aptabio Therapeutics Inc. has achieved the expected therapeutic exposure concentration in the monotherapy clinical trial for APX-343A, the company is pinning its hopes on efficacy signals from future combination therapy trials. The company anticipates that business development (BD) discussions will begin in earnest once the combination trial with Keytruda progresses to a certain stage and anticancer efficacy is confirmed.

CEO Lee said, “We are currently at the stage of confirming that the drug is delivered properly in humans,” adding, “We expect that discussions regarding technology licensing will be possible once the combination therapy trial reaches the midpoint and meaningful efficacy data is secured.”

CEO Lee remarked, “I felt a profound need for new drug development after witnessing my family member’s dialysis treatment, vision loss due to macular degeneration, and the child of an acquaintance who passed away from leukemia,” adding, “Even now, many patients are suffering because there are no treatments available. Delivering effective medications to patients as soon as possible is why we develop new drugs.”