Serina Therapeutics Responds to FDA Clinical Hold on SER-252 Parkinson's Disease Treatment
Key Insights
Serina Therapeutics submitted a complete response to the FDA's clinical hold letter for SER-252, addressing concerns about the formulation excipient trehalose.
The FDA clinical hold does not relate to the apomorphine active drug substance or its mechanism of action, maintaining the 505(b)(2) development pathway.
The company targets first-patient-in for the Phase 1b registrational study in Q1 2026, subject to FDA feedback and clinical hold resolution.
Serina Therapeutics has submitted a comprehensive response to the U.S. Food and Drug Administration's clinical hold letter for SER-252, the company's investigational apomorphine therapy for advanced Parkinson's disease. The biotechnology company announced on December 10, 2025, that it addressed FDA concerns regarding a commonly used formulation excipient, with plans to initiate the Phase 1b registrational study in Q1 2026.
FDA Clinical Hold Details
The FDA placed Serina's Investigational New Drug (IND) application for SER-252 on clinical hold pending additional information related to a formulation excipient. On November 25, 2025, the FDA issued a formal full clinical hold letter specifying the information required to permit initiation of the planned Phase 1b registrational study, designated SER-252-1b.
Importantly, the issues identified by the FDA do not relate to the apomorphine active drug substance, its mechanism of action, the use of the enFuse device from Enable Injections, or the broader 505(b)(2) New Drug Application development pathway previously discussed with the Agency.
Company Response Strategy
Serina's complete response, submitted on December 9, 2025, includes two key components. First, a detailed data package supporting the proposed use of trehalose as a subcutaneous excipient at the intended dose, including comparative information to approved products containing trehalose and additional nonclinical analyses. Second, a revised protocol to initiate the single ascending dose (SAD) phase of the SER-252-1b trial.
"Our priority has been to respond thoroughly and constructively to the FDA's requests," said Steve Ledger, Chief Executive Officer of Serina Therapeutics. "We believe our submission directly addresses the FDA's questions on trehalose, and we appreciate the Agency's continued engagement as we work toward initiating the registrational SER-252-1b trial."
Global Development Timeline
While dosing cannot begin until the clinical hold is lifted, Serina continues site start-up and regulatory activities in Australia and other regions as part of the global registrational program. In Australia, early interactions with investigators and the Parkinson's community have helped build strong support for the trial design and its potential to address unmet needs in advanced disease.
The company now expects first-patient-in (FPI) in Q1 2026, subject to timely resolution of the clinical hold and customary regulatory and ethics approvals. Initiation of the SAD phase of the SER-252-1b trial is anticipated to begin in Q1 2026.
SER-252 Therapeutic Profile
SER-252 is an investigational apomorphine therapy developed with Serina's POZ platform and designed to provide continuous dopaminergic stimulation (CDS). CDS has been shown to reduce the severity of levodopa-related motor complications (dyskinesia) in Parkinson's disease. Preclinical studies support the potential of SER-252 to provide CDS without skin reactions.
POZ Platform Technology
Serina's proprietary POZ technology is based on a synthetic, water soluble, low viscosity polymer called poly (2-oxazoline). The POZ technology is engineered to provide greater control in drug loading and more precision in the rate of release of attached drugs delivered via subcutaneous injection.
The therapeutic agents in Serina's product candidates are typically well-understood and marketed drugs that are effective but are limited by pharmacokinetic profiles that can include toxicity, side effects and short half-life. Serina believes that by using POZ technology, drugs with narrow therapeutic windows can be designed to maintain more desirable and stable levels in the blood.
Serina's POZ platform delivery technology has potential for use across a broad range of payloads and indications. The company intends to advance additional applications of the POZ platform via out-licensing, co-development, or other partnership arrangements, including the non-exclusive license agreement with Pfizer, Inc. to use Serina's POZ polymer technology for use in lipid nanoparticle drug (LNP) delivery formulations.