SHY Therapeutics Doses First Patient in Phase I Trial of Novel 19S Proteasome Inhibitor SHY-ONC6 for Solid Tumors
Key Insights
SHY Therapeutics (search) has dosed the first patient in the Luca-1 Phase I trial of SHY-ONC6 (search), a first-in-class oral 19S proteasome inhibitor, on June 29, 2026.
Unlike approved proteasome inhibitors that target the 20S catalytic core, SHY-ONC6 (search) targets AAA+ ATPase subunits within the 19S regulatory particle (search), potentially overcoming resistance mechanisms in solid tumors.
The multicenter dose-escalation and expansion study will enroll approximately 30 patients with advanced or metastatic solid tumors across nine tumor types, with initial data expected in 2027.
SHY Therapeutics (search), a New York-based biotechnology company, has dosed the first patient in Luca-1, a first-in-human Phase I clinical trial evaluating SHY-ONC6 (search), an oral small molecule that targets the 19S regulatory particle (search) of the 26S proteasome in patients with advanced or metastatic solid tumors. The first patient was enrolled on June 29, 2026, at one of three recruiting sites in Denver, Houston, and San Antonio. The trial is registered as NCT07705334 and is expected to complete in May 2028.
The milestone marks the first clinical evaluation of a proteasome inhibitor directed at the 19S regulatory particle (search) rather than the 20S catalytic core, the target of all currently approved agents in this class.
A Mechanistic Departure from Approved Proteasome Inhibitors
Proteasome inhibition has been an established therapeutic strategy in oncology since bortezomib (Velcade) earned its first FDA approval in 2003, with carfilzomib (Kyprolis) and ixazomib (Ninlaro) following. These agents all target the 20S catalytic core of the 26S proteasome, preventing the degradation of ubiquitinated proteins and triggering proteotoxic stress and apoptosis in cancer cells. While they have transformed treatment for multiple myeloma and certain lymphomas, every approval in this class remains confined to hematologic malignancies.
Efforts to extend proteasome inhibition into solid tumors have faced persistent challenges, attributable to a combination of biological resistance and dose-limiting toxicities. SHY Therapeutics (search) is betting that this confinement reflects a design limitation rather than a biological ceiling.
SHY-ONC6 (search) takes a mechanistically distinct approach by targeting the 19S regulatory particle (search), which sits upstream of the 20S catalytic core and is responsible for recognizing, unfolding, and delivering ubiquitinated proteins for degradation. The drug selectively inhibits AAA+ ATPase subunits within the 19S complex, aiming to disrupt proteasome function at an earlier stage than existing therapies. Researchers have proposed that targeting the 19S regulatory particle could overcome some mechanisms of resistance to 20S inhibitors and produce a distinct anti-tumor profile, though this approach remains experimental and has yet to be validated in clinical studies.
Luca-1 Trial Design and Endpoints
The Luca-1 study is an open-label, multicenter Phase I trial consisting of two parts. Phase Ia employs a dose-escalation design using accelerated titration and a Bayesian optimal interval design to identify the maximum tolerated dose. Phase Ib is a dose-expansion phase that will evaluate SHY-ONC6 (search) in disease-specific cohorts.
SHY-ONC6 (search) is administered orally once daily in 21-day cycles. The trial plans to enroll approximately 30 patients aged 18 years or older with advanced or metastatic solid tumors whose disease has progressed on, or who are intolerant to, standard therapies. Eligible tumor types include triple-negative breast cancer (search), colorectal cancer (search), gastric cancer, hepatocellular carcinoma, non-small cell lung cancer (search), mesothelioma, pancreatic cancer (search), prostate cancer, and soft tissue sarcoma.
Primary endpoints include determination of the maximum tolerated dose and recommended Phase II dose, as well as assessments of dose-limiting toxicities and adverse events. Secondary endpoints encompass objective response rate, duration of response, progression-free survival, overall survival, and pharmacokinetic parameters including area under the plasma concentration-time curve, maximum plasma concentration, and elimination half-life.
Timeline and Strategic Implications
Initial data from the Luca-1 trial are expected in 2027, representing an approximately 18-month window from first dose to first readout. This timeline is consistent with a normal pace for a solid tumor dose-escalation study, but it means SHY Therapeutics (search) will be operating on preclinical credibility alone for an extended period before investors or partners can evaluate clinical signal.
The company's broader platform targets ATPases and GTPases across oncology and infectious disease, positioning Luca-1 as simultaneously a proof-of-concept for SHY-ONC6 (search) and a real-world stress test of the platform's core hypothesis. The single number worth tracking as the trial advances, according to analysts, is the dose at which SHY-ONC6 achieves pharmacodynamic evidence of 19S inhibition in patients. That threshold will determine whether the tolerability advantage observed in preclinical solid tumor models translates to humans or represents an artifact of species differences. Without a confirmed active dose in humans, the mechanistic story remains theoretical.
The company has not disclosed any partnerships or external funding related to the SHY-ONC6 (search) program.