Safety of Intravenous Neridronic Acid in CRPS

Inclusion Criteria

• Informed consent signed.
• Male or female participant at least 18 years of age at Visit 1.
• A diagnosis of complex regional pain syndrome according to the clinical diagnostic criteria recommended by the International Association for the Study of Pain (IASP; "Budapest clinical criteria"), assessed at Visit 1. Signs and symptoms of CRPS must apply to an affected limb (arm or leg) and must demonstrate asymmetry with respect to the contralateral limb.
• Ongoing moderate to severe chronic pain, including a baseline current pain intensity score of greater than or equal to 4 using an 11-point Numerical Rating Scale, referring to the CRPS-affected limb, at Visit 2 (prior to dosing).
• In stable treatment and follow-up therapy for CRPS for at least 1 month prior to allocation to treatment (Visit 2). Participants must have failed trials of at least 2 treatments for CRPS, one of which must be a pharmacologic treatment.
• Women of child-bearing potential must have a negative urine beta-human chorionic gonadotropin (β-HCG) pregnancy test at Visit 1 and must be using 2 forms of medically acceptable contraception, including at least 1 highly effective method of contraception with a low failure rate, defined as less than 1% per year (e.g., oral contraceptives or intrauterine device), and a second medically acceptable method such as use of condoms with spermicide by their male partner. A barrier method alone is not acceptable. Highly effective methods of contraception must be used for at least 1 month prior to Visit 2 and for the duration of the trial.
• Participants must be able to communicate meaningfully, be able to differentiate with regard to location and intensity of the pain, and be able to answer the questions in the questionnaires used in this trial (assistance in filling out the questionnaires may be provided, if required due to motor or other impairment).

Exclusion Criteria

• Evidence of renal impairment (estimated glomerular filtration rate [eGFR] less than 60 mL/min/1.73 m2 using the 2009 Chronic Kidney Disease Epidemiology Collaboration [CKD-EPI] creatinine equation [Levey et al. 2009] or a urinary albumin creatinine ratio greater than 150 mg/g), based on central safety laboratory data obtained prior to Visit 2, or a history of chronic kidney disease. Note: a single repeat laboratory test is allowed.
• Serum calcium or magnesium outside of the central laboratory's reference range, based on central safety laboratory data obtained prior to Visit 2 (a single repeat laboratory test is allowed); a history of hypocalcemia or a metabolic disorder anticipated to increase risk for hypocalcemia (e.g., hypoparathyroidism); concomitant use of drug(s) with known potential to cause hypocalcemia (e.g., aminoglycosides).
• Vitamin D deficiency, defined as a 25(OH)D level less than 30 ng/mL, based on central safety laboratory data obtained prior to Visit 2 (up to 4 repeat laboratory tests are allowed). Participants with vitamin D deficiency should receive appropriate supplementation during the enrollment period. A vitamin D level of at least 30 ng/mL must be documented prior to allocation to investigational medicinal product (IMP).
• Corrected QT interval (according to Fridericia's formula; QTcF) greater than 470 ms (average of 3 electrocardiograms [ECGs] obtained at Visit 1); serum potassium outside the central laboratory's reference range at Visit 1; clinically unstable cardiac disease, including: unstable atrial fibrillation, symptomatic bradycardia, unstable congestive heart failure, active myocardial ischemia, or an indwelling pacemaker; evidence of complete left bundle branch block; complete atrioventricular block; history of Long QT Syndrome or a relative with this condition; or any other known risk factor for torsade de pointes.
• Participants receiving medications with a known risk of torsades de pointes within 7 days prior to allocation. Participants receiving selective serotonin re-uptake inhibitor antidepres