Phase 3 Trial Brings Hope to a Long-Ignored Condition

Ambros Therapeutics doses its first patient in a Phase 3 trial testing neridronate for Complex Regional Pain Syndrome Type 1

8 Jun 2026

Ambros Therapeutics has begun a Phase 3 clinical trial of neridronate, a compound under investigation for Complex Regional Pain Syndrome Type 1 (CRPS-1), a chronic neuro-inflammatory condition affecting an estimated 65,000 Americans. No treatment has yet received regulatory approval for the disease.

CRPS-1 causes persistent, severe pain that is poorly understood and difficult to treat. The condition involves abnormal signalling between the nervous system and surrounding tissue, often following an injury. Patients typically have limited recourse beyond general pain management.

Neridronate, originally developed as a bone-active agent, is thought to reduce localised tissue inflammation and disrupt the chronic pain signals associated with CRPS-1. The Phase 3 study will measure both safety and long-term clinical improvement across multiple international sites, using standardised pain mapping alongside real-world patient data.

Approval, if it comes, would represent the first disease-specific therapy for CRPS-1, a category that has drawn limited pharmaceutical investment given its relatively small patient population and complex underlying biology.

Whether positive results would encourage broader investment in neuro-inflammatory rare diseases remains an open question. The field has seen increased interest from smaller biotechnology firms in recent years, though late-stage failures remain common.

Regulatory clearance will depend on the strength of evidence the trial produces. Demonstrating durable physiological improvement over time is expected to be the central requirement for submissions to bodies such as the US Food and Drug Administration.