US-based Protalex has received approval from the French National Agency for Medicines and Health Products (ANSM) for its clinical trial application to begin a Phase Ib trial of its lead drug candidate PRTX-100.

PRTX-100 is a new-generation, immunomodulatory therapy and a highly purified form of Staphylococcal protein A (SpA), which is being evaluated to treat autoimmune diseases, such as rheumatoid arthritis (RA) and persistent / chronic immune thrombocytopenia (ITP).

SpA is a bacterial protein demonstrated by Protalex and others to affect immune function in several preclinical trials.

The approval allows the company to start the trial (PRTX-100-203 Study) at several sites in France with patient enrolment expected to begin before the year-end.

In addition, the Committee for Orphan Medicinal Products (COMP) of the European Medicines Agency (EMA) has issued a positive opinion, recommending PRTX-100 for use as an orphan medicinal product to treat ITP.

"The 203 Study is designed to evaluate the safety and efficacy of PRTX-100 in a range of doses."

The approval to start the trial and the positive COMP opinion follows the company’s previously announced initiation of a US Phase I / II clinical trial of PRTX-100 in adult ITP patients (PRTX-100-202 Study) and receipt of orphan drug designation (ODD) for the drug to treat ITP from the US Food and Drug Administration (FDA).

Protalex ITP Programmes vice-president Richard Francovitch said: "The 203 Study is designed to evaluate the safety and efficacy of PRTX-100 in a range of doses and, along with the recently initiated US-based 202 Study, will provide important data to support further development plans in ITP.

"Protalex is also very pleased to have received a positive opinion from the EMA COMP on the PRTX-100 application for ODD.

"Based on preclinical observations and data generated in prior clinical trials in patients with RA, we believe PRTX-100 represents a promising new approach for the treatment of ITP."

Approximately 30 patients will be enrolled in the open-label, dose-escalating 203 study in as many as five cohorts. Each patient will be given four, weekly intravenous doses of PRTX-100 and will be monitored for up to 48 weeks thereafter.

The trial’s primary endpoint is safety, while secondary endpoints include platelet response to PRTX-100, immunogenicity and pharmacokinetics.