Pamplona, Navarra – 23 October 2026 – Palobiofarma announced results from its Phase 2 study of PBF-999, its investigational PDE10A inhibitor for the treatment of Prader-Willi syndrome (PWS), presented at the Foundation for Prader-Willi Research (FPWR) Research Symposium on 8 October in Philadelphia.
The results provide the first clinical evidence supporting PDE10A inhibition as a potential therapeutic approach in PWS. In the placebo-controlled phase of the study, treatment with PBF-999 was associated with statistically significant differences versus placebo in hyperphagia, body weight and several metabolic measures assessed in the study. Continued treatment was associated with further changes across these domains, providing additional support for the continued clinical development of PBF-999.
Presenting the results at the FPWR Research Symposium, Santiago Figueroa, COO of Palobiofarma, said: “We are very encouraged by the consistency of the clinical signals observed across hyperphagia, body weight and metabolic outcomes. These findings provide encouraging clinical support for our therapeutic approach and support the continued development of PBF-999 towards a pivotal Phase 3 programme.”
“The Phase 2 results strengthen our conviction in PBF-999 and mark an important step in the development of the programme,” said Julio Castro, CEO of Palobiofarma. “Our priority now is to translate these encouraging findings into a successful late-stage development programme. We are committed to moving PBF-999 forward with urgency and rigour, with the ultimate goal of making a new treatment option available to the PWS community, subject to successful clinical development and regulatory approval.”
A differentiated approach to Prader-Willi syndrome
PBF-999 is an investigational inhibitor of PDE10A, an enzyme involved in pathways relevant to food intake and energy metabolism. Palobiofarma is investigating whether PDE10A inhibition may influence central pathways involved in hyperphagia and food intake, as well as peripheral pathways involved in energy metabolism, providing the rationale for evaluating PBF-999 across multiple manifestations of PWS.
The Phase 2 study evaluated PBF-999 in adults and adolescents with genetically confirmed PWS using a randomised, blinded crossover design followed by an open-label extension.
PBF-999 showed a manageable safety profile. Treatment-related events that were severe or led to discontinuation were uncommon and resolved without sequelae.
Advancing towards Phase 3
Based on the Phase 2 findings, Palobiofarma is planning a larger, adequately powered, multinational, multicentre, randomised, placebo-controlled Phase 3 study to confirm the efficacy findings, establish the optimal dose and further characterise the safety profile of PBF-999.
The programme represents an opportunity to further investigate a differentiated therapeutic approach with the potential to address several important manifestations of PWS, including hyperphagia, body weight and metabolic dysfunction.
About PBF-999
PBF-999 is an investigational PDE10A inhibitor being developed by Palobiofarma for Prader-Willi syndrome. The Phase 2 findings provide clinical evidence supporting further evaluation of PDE10A inhibition as a potential therapeutic approach in PWS.
PBF-999 is an investigational medicine and has not been approved for the treatment of Prader-Willi syndrome or any other indication. Its safety and efficacy have not been established.
About Palobiofarma
Palobiofarma is a clinical-stage biopharmaceutical company focused on the discovery and development of novel therapies for diseases with significant unmet medical needs.