U.S. REGULATORY STATUS · AUGUST 12, 2026
FDA approval
& neridronate
Neridronate is not FDA-approved for CRPS in the United States yet. The FDA’s own Orphan Drug database currently lists neridronate as designated for CRPS but explicitly states: “Not FDA Approved for Orphan Indication.”
What is already significant is the development status: neridronate has received Orphan Drug, Fast Track and Breakthrough Therapy designations, and a pivotal Phase 3 trial — CRPS-RISE — is underway in the United States.
CURRENT U.S. STATUS
NOT APPROVED YET
Development is advanced, but FDA marketing approval has not been granted.
✓
Orphan Drug designation
FDA designation recorded March 25, 2013.
✓
Fast Track designation
Expedited-development pathway granted during the U.S. program.
✓
Breakthrough Therapy designation
FDA designation for an investigational drug with promising preliminary clinical evidence.
●
Phase 3 CRPS-RISE
Ongoing pivotal randomized, triple-blind, placebo-controlled trial.
—
FDA marketing approval
Not granted as of the status date above.
FDA DATABASE · VERIFIED AUGUST 12, 2026
“Not FDA Approved for Orphan Indication”
The official FDA Orphan Drug Designations and Approvals database lists neridronate for treatment of CRPS-1, CRPS-II and CRPS-NOS as Designated, while the approval field remains Not FDA Approved for Orphan Indication.
WHAT THE FDA HAS ALREADY GRANTED
Three important designations — none of them is marketing approval.
These programs matter because they show that neridronate entered special FDA pathways intended to support development of therapies for serious conditions, unmet medical need and rare diseases. But designation and approval are different regulatory events.
01
2013
Orphan Drug
FDA granted orphan designation to neridronate on March 25, 2013 for treatment of complex regional pain syndrome.
WHAT IT SIGNALS
Development for a rare disease or condition.
WHAT IT DOES NOT MEAN
Orphan designation is separate from FDA approval.
02
EXPEDITED
Fast Track
Fast Track is designed by FDA to facilitate development and expedite review of drugs intended to treat serious conditions and fill an unmet medical need.
WHAT IT SIGNALS
More frequent FDA interaction and potential rolling review.
WHAT IT DOES NOT MEAN
Fast Track does not establish that FDA has found the drug safe and effective for marketing.
03
BREAKTHROUGH
Breakthrough Therapy
FDA describes Breakthrough Therapy designation as an expedited-development process for drugs intended to treat a serious condition when preliminary clinical evidence indicates that the drug may demonstrate substantial improvement over available therapy on a clinically significant endpoint.
WHAT IT SIGNALS
Intensive FDA guidance and organizational commitment during development.
WHAT IT DOES NOT MEAN
A Breakthrough Therapy designation is not the same as FDA approval.
WHAT THESE DESIGNATIONS ACTUALLY MEAN
FDA has created a faster development pathway — not a lower scientific standard.
FDA’s own materials state that expedited programs are intended to help promising therapies move efficiently through development and review. They do not remove the need for evidence supporting safety and effectiveness before approval.
01
More interaction with FDA
Fast Track and Breakthrough Therapy programs can increase communication between the sponsor and FDA about clinical development and review.
02
Potentially more efficient review
Fast Track can make a drug eligible for rolling review, allowing completed parts of a future NDA to be submitted before every section is complete.
03
FDA has seen enough evidence to grant the designation
Breakthrough Therapy requires preliminary clinical evidence indicating that a drug may demonstrate substantial improvement over available therapy on a clinically significant endpoint.
04
The approval standard still applies
A future marketing application must still support FDA conclusions about safety, effectiveness, benefit-risk, labeling and manufacturing quality.
WHERE THE U.S. PROGRAM IS NOW
CRPS-RISE: the pivotal Phase 3 study
ClinicalTrials.gov lists CRPS-RISE as a Phase 3 multicenter, randomized, triple-blind, placebo-controlled trial evaluating IV neridronate in adult participants with selected warm CRPS-I.
01
Phase 3
Pivotal development stage
The trial is designed to assess efficacy, safety and tolerability.
02
~270
Planned participants
Participants are randomized to IV neridronate or placebo.
03
400 mg
Total IV neridronate dose
Treatment is administered on Days 1, 4, 7 and 10.
04
Week 12
Primary pain endpoint
The program evaluates change in pain intensity from baseline to week 12.
STUDY ID · NCT07210515
A precision-selected warm CRPS-I population
The registered study focuses on adult participants with warm CRPS-I and a positive triple-phase bone scan. The trial uses a placebo-controlled design to test whether neridronate can reproduce clinically meaningful benefit in the population selected for the U.S. registrational program.
April 2026
Study start listed in current trial records.
June 8, 2026
Ambros announced the first participant dosed.
August 2026
Phase 3 program ongoing.
Future milestone
Results must support a future regulatory application before approval can be considered.
WHAT STILL HAS TO HAPPEN
Phase 3 is not the approval. It is evidence intended to support the approval process.
FDA describes the New Drug Application — NDA — as the formal vehicle through which a sponsor asks the agency to approve a new pharmaceutical for sale and marketing in the United States.
IF FDA EVENTUALLY APPROVES NERIDRONATE
Approval would be a specific regulatory decision — with an indication, label and conditions of use.
An FDA approval is not a generic endorsement of every possible use of a drug. It is tied to the indication and labeling that FDA approves after reviewing the submitted evidence.
01
A U.S. approved indication
FDA would define the population and use for which the evidence supports marketing.
02
FDA-approved prescribing information
The label would describe dosing, safety information, warnings and other conditions of use.
03
Reviewed manufacturing quality
FDA’s NDA review includes whether manufacturing methods and quality controls are adequate.
04
Post-market safety monitoring
FDA continues monitoring safety after approved drugs become available to the public.
05
It would not mean every patient responds
Regulatory approval establishes an acceptable benefit-risk profile for the approved use, not a guarantee of individual treatment success.
06
Until FDA acts, use the word “investigational” in the U.S.
The current U.S. status should not be described as approved, authorized or cleared for CRPS.
PHASE 3 CLINICAL TRIAL
Neridronate is investigational in the U.S.
Drug approval is jurisdiction-specific. A medicine’s regulatory status in one country does not automatically transfer to another country’s drug agency.
UNITED STATES
INVESTIGATIONAL
FDA approval for CRPS has not yet been granted.
The current U.S. program is in pivotal Phase 3 development with FDA expedited development designations.
COMMON REGULATORY CONFUSION
These phrases sound similar. They are not interchangeable.
The distinction matters because patients should be able to tell the difference between scientific evidence, an FDA development designation, a clinical trial and an actual marketing approval.
01
“FDA designated”
The drug received a development designation such as Orphan Drug, Fast Track or Breakthrough Therapy.
02
“Phase 3”
The drug is being tested in late-stage clinical development intended to generate evidence that may support a regulatory application.
03
“Approved in Italy”
The drug has marketing approval in Italy under the Italian regulatory framework.
04
“FDA approved for CRPS”
This statement should only be used after FDA has formally approved the relevant U.S. marketing application and indication.
Not true yet
PATIENT SUPPORT
Separate three questions: Does the evidence support neridronate?What is its current FDA status?
Carla Crowe, Patient Care Coordinator – California, can help patients locate CRPS Support resources, scientific documentation and practical information about treatment. U.S. regulatory status should always be verified against current FDA and ClinicalTrials.gov records.
CARLA CROWE
Patient Care Coordinator – California
CURRENT STATUS SHOULD BE STATED EXACTLY.