KING OF PRUSSIA, PA — SEED Therapeutics Inc. took a critical step from laboratory promise to human testing with the first patient dosed in a Phase 1a study of ST-01156, an experimental oral cancer drug designed to dismantle a key protein that many aggressive tumors rely on to survive.
The drug, a so-called molecular glue degrader, targets RBM39, a central regulator of RNA splicing and gene transcription. By selectively degrading that protein, ST-01156 aims to cripple cancer cells at a fundamental biological level rather than merely blocking a single signaling pathway. The approach places SEED in the fast-moving field of targeted protein degradation, one of the most closely watched frontiers in oncology drug development.
The open-label, dose-escalation trial will enroll patients with advanced solid tumors, with a focus on cancers that have shown strong dependence on RBM39 in preclinical research. Those include Ewing sarcoma, KRAS-mutant cancers, and hepatocellular carcinoma, three areas where effective treatment options remain limited.
ST-01156 is taken orally once a day for five days out of every seven, across four-week treatment cycles. The initial goal of the trial is to determine safety, tolerability, and the appropriate dose for later-stage studies. Researchers will also track how the drug moves through the body, whether it hits its intended molecular target, and whether it shows early signs of shrinking tumors.
SEED’s decision to push into human testing follows a set of unusually strong laboratory results. In animal models, ST-01156 produced complete tumor regression in both Ewing sarcoma and KRAS-mutant colorectal cancer, while maintaining what the company described as a favorable safety profile. Those data persuaded regulators to grant the drug both Orphan Drug and Rare Pediatric Disease designations for Ewing sarcoma, a rare but devastating cancer for which no new therapy has been approved in three decades.
“Dosing the first patient with ST-01156 marks an important milestone for SEED and for patients with cancers that urgently need new therapeutic options,” said Dr. Lan Huang, co-founder and chief executive of SEED Therapeutics. She said the company believes RBM39 degradation could emerge as a “powerful and differentiated” treatment strategy.
Independent experts also see the study as a meaningful test of a new therapeutic concept. George Demetri, a Harvard Medical School professor and chair of SEED’s scientific advisory board, said the trial is designed to generate not just safety data but also detailed pharmacokinetic, pharmacodynamic, and biomarker insights that could accelerate development.
“The initiation of clinical dosing brings us one step closer to translating the novel mechanism of ST-01156 action into meaningful benefit for patients,” Demetri said.
The trial is being conducted at a network of elite cancer centers, including Dana-Farber, Memorial Sloan Kettering, MD Anderson, Mass General, City of Hope, and Hoag Cancer Center, reflecting the high level of scientific and clinical interest in the program.
For SEED Therapeutics, the first human dose is more than a procedural milestone. It is a test of whether a bold bet on RNA-focused protein degradation can deliver a new class of cancer medicines, and whether the dramatic effects seen in animals can survive the unforgiving transition to human biology.
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