Pamplona, Spain – May 11st, 2026 – Palobiofarma S.L., a biopharmaceutical company focused on the discovery and development of innovative treatments for orphan diseases, today announced significant progress in the clinical development of PBF‑999, its novel PDE10 inhibitor for the treatment of Prader‑Willi Syndrome (PWS).

The Company has achieved two major milestones:

• Successful completion of Phase 2 clinical trial in 32 patients aged 12 years and older, demonstrating a clinically meaningful reduction in hyperphagia and confirming a favourable safety and tolerability profile.
• Completion of successful End-of-Phase 2 Meeting with the US FDA and EMA paving the way to advancing product development towards Phase 3 initiation.

The Phase 2 pilot study was conducted at University Hospital Parc Taulí in Sabadell, Spain, under the leadership of Dr. Assumpta Caixàs, Chair of the Prader‑Willi Syndrome Group of the Spanish Society of Obesity. The study evaluated the safety, tolerability, and preliminary efficacy of PBF‑999 in adolescent and adult patients living with PWS, a rare and severe genetic disorder characterized by hyperphagia, cognitive impairment, and behavioural challenges.

Data from the study demonstrated that PBF‑999 meaningfully reduced hyperphagic behaviours, one of the most debilitating symptoms of PWS, while maintaining a consistent safety profile across main patient subgroups.

These results were presented to the FDA and EMA as part of an End‑of‑Phase 2 Meeting, during which the Agency provided constructive feedback on the design features, primary and secondary endpoints, and overall regulatory path for the pivotal Phase 3 clinical program.

“We are very pleased with the constructive and encouraging dialogue with the FDA regarding the development of PBF‑999 for Prader‑Willi Syndrome,” said Dr. Julio Castro‑Palomino, CEO of Palobiofarma. “Receiving Agency feed-back on the critical components of the Phase 3 program represents a major milestone for the Company. We remain fully committed to initiating this pivotal study early 2027.”

PBF‑999, discovered by Palobiofarma, is a first‑in‑class PDE10 inhibitor that has shown potent and selective enzyme inhibition in preclinical models. PDE10 plays a key regulatory role in neuronal signalling pathways involving cyclic nucleotides.

To date, PBF‑999 has been evaluated in three clinical studies, consistently demonstrating appetite suppressant activity and a favourable safety and tolerability profile.

Palobiofarma remains committed to developing transformative therapies for patients living with severe and underserved rare diseases, and the advancement of PBF‑999 represents a significant step forward in addressing the urgent unmet medical needs of individuals with Prader‑Willi Syndrome.