[Edaily Reporter YU JIN-HEE ] A decisive breakthrough that could shatter the “therapeutic ceiling” of targeted anticancer drugs—a challenge modern oncology has faced for over 80 years—has been revealed by a team of Korean researchers. This new paradigm in cancer treatment overcomes “pseudo-resistance”—which was caused not by cancer cell mutations but by matrix barriers in the tumor microenvironment (TME)—and dramatically restores the efficacy of standard therapies.

Innovative New Drug Development Biotech #PenetriumBio held the “Penetrium Global Clinical Development Symposium 2026” on the 14th at the Grand InterContinental Seoul Parnas in Gangnam-gu, Seoul, and made a surprise announcement regarding efficacy data from patient-derived three-dimensional (3D) cancer organoids for its core pipeline, “Penetrium,” as well as its strategy to proceed directly to a U.S. Phase 2 clinical trial.

Fully Restoring the Efficacy of Targeted Therapies Neutralized by the Cancer-Associated Fibroblast (CAF) Barrier

The core of the presentation was the use of clear quantitative data to elucidate the origins of the therapeutic limitations of “daraxonrasib,” a latest-generation RAS-targeted anticancer drug, and how Penetrium overcomes them.

The study was conducted in collaboration with MBD, a company specializing in 3D cell culture platforms, using tissue samples derived from lung and ovarian cancer patients. According to the analysis data, when daraxonrasib was administered alone to lung cancer organoids derived from patients, the cancer cell survival rate was suppressed to 57.8%.

However, when a dense matrix barrier formed by cancer-associated fibroblasts (CAFs)—mirroring conditions inside the patient’s body—was added, the cancer cell survival rate soared to 89.6% even at the same dosage. This was not the result of genetic resistance but rather “pseudo-resistance,” in which the matrix barrier physically and biochemically blocked the drug’s deep penetration.

A dramatic turnaround was observed in the Penitrium combination group. When Penitrium—which independently targets this pseudo-resistance—was administered alongside Darlasonrasip, the cancer cell survival rate, which had soared to 89.6%, plummeted to just 7.5%. This demonstrated a far more potent cytotoxic effect than the rate observed with Darlasonrasip alone in a normal stromal environment (57.8%).

The same results were observed in ovarian cancer organoids. While the survival rate was 50.5% with Daraxsonrasip alone, it rose to 67.7% when combined with the CAF barrier; however, it plummeted to 12.8% upon co-administration of Penitrium. This demonstrates the drug’s versatility, proving it can be widely applied to various solid tumors that form a tumor microenvironment, not limited to specific cancer types.

While existing combination therapies involved mixing anticancer drugs with different mechanisms of action to attack cancer cells from multiple angles, Penitrium has established the concept of “Concurrent Parallel Targeting,” in which existing targeted therapies strike the cancer cells while Penitrium breaks down the barriers that block their efficacy.

Based on its preclinical results, PenetriumBio has obtained an Investigational New Drug (IND) approval from the U.S. Food and Drug Administration (FDA) and is proceeding directly to a Phase 2a clinical trial for patients with advanced solid tumors. Skipping the typically required Phase 1 trial and moving directly to Phase 2 to verify efficacy is a decisive turning point that shortens the new drug development timeline by several years.

This direct progression to Phase 2 was made possible not by bypassing standard drug development procedures, but thanks to the extensive human safety profile already accumulated. A drug with the same active ingredient and formulation as Penitrium has already generated human administration data from over 300 patients in domestic clinical trials alone during the COVID-19 pandemic. Currently, it is also progressing smoothly through Phase 2 and 3 clinical trials in Vietnam as a treatment for dengue fever, where its safety, tolerability, and pharmacokinetics (PK) in humans have been firmly validated.

Under FDA regulations, substances for which human safety and toxicity evaluation data have been sufficiently demonstrated for other indications are officially permitted to proceed directly to Phase 2 clinical trials—which evaluate efficacy for the target disease—without undergoing a duplicative Phase 1 trial.

There are numerous global precedents where companies have leveraged their established safety profiles to proceed directly to Phase 2 clinical trials for anticancer drugs. The antihypertensive drug “Losartan” was immediately enrolled in a Phase 2 clinical trial in combination with “Folfirinox” for patients with locally advanced pancreatic cancer, based on recognition of its tumor stroma-modulating mechanism. The diabetes drug “Metformin” also proceeded directly to a randomized Phase 2 trial for pancreatic cancer based on extensive clinical data and successfully demonstrated its efficacy.

A local clinical team led by Kim Taek-sung, President of PenetriumBio’s U.S. Operations, in collaboration with a U.S.-based contract research organization (CRO) specializing in regulatory affairs, successfully implemented a protocol designed based on this evidence.

In particular, by incorporating a “Safety Lead-in” approach—which first assesses the safety of combination therapy and identifies any dose-limiting toxicities (DLTs) in an early patient cohort—they thoroughly implemented the safety measures required by regulatory authorities.

World-Class Experts Assembled… Pursuing a “Big Deal” Ahead of Keytruda’s Patent Expiration in 2028

The company envisions that entering this U.S. Phase 2 clinical trial will complete a “three-pronged approach” aimed at maximizing development speed, approval probability, and technological value. The first is “speed.” By skipping the Phase 1 process, the company saved at least one to two years and tens of billions of won in costs. The dosage to be used in the U.S. Phase 2 trial has been designed to be significantly lower than the maximum safe dose confirmed in infectious disease clinical trials. The company is enhancing data precision through a “Korea-U.S. parallel two-track” system, in which the optimal dosage is precisely determined via an independent Phase 1 anticancer trial currently underway in Korea.

Second is the “probability of approval.” The company has preemptively eliminated unpredictable toxicity variables, a primary cause of new drug development failures. Furthermore, a world-class research team has been assembled. Professor Sandip Patel, who led the rare cancer basket trial (DART) at the Moores Cancer Center at the University of California, San Diego (UCSD), serves as the Principal Investigator (PI). Gary S. Firestein, UCSD Distinguished Professor and a world-renowned expert in the tumor microenvironment and rheumatology, has joined the project to form the “Tumor and Autoimmune Microenvironment Advisory Committee,” thereby doubling the clinical credibility of the study.

Third is the “market value transformation.” Similar to the “CIAAT & Soil” theory proposed by Stephen Paget in 1889, unlike existing treatments that only attack cancer cells (the “CIAAT”), Penitrium fundamentally normalizes the damaged tumor microenvironment (the “soil”) through generative artificial intelligence (AI).

Notably, the U.S. substance patent for “Keytruda” (generic name: pembrolizumab), an immunotherapy drug from Merck (MSD)—the world’s top-selling pharmaceutical company—expires in 2028. Global pharmaceutical companies are staking their survival on securing next-generation combination partner drugs to defend against the patent cliff. PenetriumBio’s strategy is to secure Phase 2 clinical efficacy data early on and secure a large-scale technology licensing (L/O) agreement with a global big pharma company in time for the patent expiration.

Cho Won-dong, Chairman of PenetriumBio, emphasized, “Skipping directly to a U.S. Phase 2 clinical trial is not merely a matter of shortening the development timeline; it is a sophisticated strategic move designed to maximize the success rate based on scientifically validated data.” He added, “Based on the clinical leadership of world-renowned experts and our unique mechanism of action targeting pseudo-resistance, we will lead a paradigm shift in the global oncology market.”