A Phase 3 interventional study of Neridronate and Placebo in Complex Regional Pain Syndrome Type I, sponsored by Ambros Therapeutics, Inc.. Recruiting at 33 sites in United States. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-10-29.
Sponsored by Ambros Therapeutics, Inc. · Phase 3, Interventional, and Treatment
Phase 3 Trial of AMBTX-01 (neridronate) for Complex Regional Pain Syndrome Type 1
This is a multicenter, randomized, triple-blind, controlled trial, to assess the efficacy, safety, and tolerability of neridronate 400 mg IV in adult participants with the warm subtype of Complex Regional Pain Syndrome Type 1 (CRPS-1) and a positive triple phase bone scan (TPBS).
The total planned trial duration for each participant will be approximately up to 18 weeks and will include:
43 studies on the registry are indexed under Reflex Sympathetic Dystrophy; 4 are open to participants now.
This study's planned enrollment of 270 is above the median of 48 across 35 interventional studies indexed under Reflex Sympathetic Dystrophy.
Browse Reflex Sympathetic Dystrophy studies →Ambros Therapeutics, Inc. is the lead sponsor of 3 studies on the registry; 3 are open to participants now.
Compared within Reflex Sympathetic Dystrophy, this study's primary condition as ClinicalTrials.gg classifies it; the registry's first condition term is Complex Regional Pain Syndromes. The counts are of registry records indexed under each term, refreshed daily. How we classify →
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Single affected limb at the Screening and Randomization Visits meeting the following warm subtype criteria:
AND ≥ 2 of the following:
Women of must:
Exception: Women exclusively engaging in same sex sexual activities are not required to meet this criterion.
Exclusion Criteria
The use of any of the following treatments within the timeframe specified from Randomization Visit:
Within the last 12 months:
Within the last 6 months:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Childbearing potential
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraception
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
400 mg AMBTX-01 infusion
Drug: Neridronate
Placebo comparator
Drug: Placebo
neridronate 100 mg, given as a 2-hour infusion on Days 1, 4, 7, and 10.
placebo comparator
Change in pain intensity from baseline to Week 12.
Assessed on an 11-point Numerical Rating Scale (NRS), with 0 representing no pain and 10 representing the worst possible pain.
Time frame: Week 12
At least a 50% reduction from baseline to Week 12 in pain intensity.
Assessed using an 11-point Numerical Rating Scale (NRS), with 0 representing no pain and 10 the worst possible pain.
Time frame: Week 12
Change from baseline in CRPS Severity Score (CSS) to Week 12.
Assessed using the CRPS CSS, a 0-16 scale where higher scores denotes greater CRPS symptom severity and lower scores reflect milder symptoms.
Time frame: Week 12
Patient Global Impression of Change (PGI-C) in CRPS-Related Health.
Assessed using the PGI-C, a 7-point numerical rating scale where 1 indicates "very much improved" and 7 indicates "very much worse."
Time frame: Week 12
Change from baseline in the Short Form 36 (SF-36) Item Health Survey Physical Functioning domain.
Assessed using the SF-36, a validated 36-item self-reported questionnaire that measures health-related quality of life across eight domains: physical functioning, role limitations due to physical health, bodily pain, general health perceptions, vitality, social functioning, role limitations due to emotional problems, and mental health. Scores range from 0 to 100, with higher scores indicating better health status.
Time frame: Week 12
Change from baseline over time in pain intensity.
Assessed on an 11-point Numerical Rating Scale (NRS), with 0 representing no pain and 10 representing the worst possible pain.
Time frame: Day 10, Weeks 3, 6, and 9
At least a 50% reduction from baseline in pain intensity.
Assessed using an 11-point Numerical Rating Scale (NRS), with 0 representing no pain and 10 the worst possible pain.
Time frame: Day 10, Weeks 3, 6, and 9
At least a 30%, 70%, and 90% reduction from baseline in pain intensity.
Assessed using an 11-point Numerical Rating Scale (NRS), with 0 representing no pain and 10 the worst possible pain.
Time frame: Day 10, Weeks 3, 6, 9, and 12
Time to onset of analgesic improvement.
Assessed as the time to onset of analgesic improvement, defined by a ≥30% reduction in pain intensity from baseline on the 11-point Numerical Rating Scale (NRS), with 0 representing no pain and 10 the worst possible pain. The improvement must be sustained for a minimum of one week.
Time frame: daily assessment up to week 12
Time to at least a 50%, 70%, and 90% reduction from baseline in pain intensity.
Assessed using an 11-point Numerical Rating Scale (NRS), with 0 representing no pain and 10 the worst possible pain.
Time frame: 7-day average
Change from baseline in the 7-day mean of daily "pain now".
Assessed on an 11-point Numerical Rating Scale (NRS), with 0 representing no pain and 10 representing the worst possible pain.
Time frame: Day 10, Weeks 3, 6, 9, and 12
At least a 30%, 50%, 70%, and 90% reduction from baseline in pain intensity.
Assessed using an 11-point Numerical Rating Scale (NRS), with 0 representing no pain and 10 the worst possible pain.
Time frame: Day 10, Weeks 3, 6, 9, and 12
Change from baseline in 7-day average mean of daily "worst pain" assessment.
Assessed using the average score from the 11-point Numerical Rating Scale (NRS), where 0 denotes no pain and 10 denotes the worst possible pain
Time frame: Day 10, Weeks, 3, 6, 9, 12
At least a 30%, 50%, 70%, and 90% reduction from baseline in pain intensity
Assessed using the average score of daily "worst pain" from the 11-point Numerical Rating Scale (NRS), where 0 denotes no pain and 10 denotes the worst possible pain
Time frame: Day 10, Weeks, 3, 6, 9, 12
Change from baseline in pain evoked by active motion.
Assessed using an 11-point Numerical Rating Scale (NRS), with 0 representing no pain and 10 the worst possible pain in the CRPS affected limb.
Time frame: Day 10, Weeks 3, 6, and 12
At least a 50% reduction from baseline in pain evoked by active motion.
Assessed using an 11-point Numerical Rating Scale (NRS), with 0 representing no pain and 10 the worst possible pain in the affected limb.
Time frame: Day 10, Weeks 3, 6, 12
Change from baseline in active range of motion (AROM) of affected limb vs. contralateral limb.
Assessed by measuring range of motion of selected joints using a goniometer, and calculating the change from baseline for each joint assessed.
Time frame: Day 10, Weeks 3, 6, 12
Change from baseline in the CRPS Severity Score (CSS) and in the individual elements of the CRPS Severity Score.
CRPS severity score is a series of 17, 0-1 questions (where 0 is that the sign/symptom is not displayed and 1 is that the sign/symptom is displayed) and scored for a total score of 0 (no CRPS signs/symptoms) to 17 (worse CRPS severity).
Time frame: Days 4, 7, 10, Weeks 3, and 6
Change from baseline in the CSS self-report (CSS-SR)
CSS-SR is a patient, self-report questionnaire that assess the same 13 concepts of the CSS using yes/no items. Responses are coded as present (1) or absent (0) and summed to yield a total score (range 0-13)
Time frame: Week 12
Change from base line in edema of affected limb
Assessed using the "edema" using 4-point numerical rating scale where 0 is no edema and 3 is severe edema.
Time frame: Days 4, 7, 10, Weeks 3, 6, and 12
Change from baseline in temperature of affected limb vs contralateral limb.
Assessment of 'temperature' is defined as the difference in temperature, measured in degrees Celsius (°C) using an infrared thermometer, between the affected limb and the contralateral limb.
Time frame: Days 4, 7, 10, Weeks 3, 6, and 12
Change from baseline in use of rescue analgesic medications.
Changes from baseline at each time point will be classified as improved (yes-to-no), unchanged (no-to-no or yes-to-yes), or worsened (no-to-yes).
Time frame: Day 10, Weeks 3, 6, 9, and 12
Change from baseline in mean daily dose of rescue analgesic medicines.
Assessed as the mean daily dose of rescue analgesic medications, calculated over the 7-day period preceding each scheduled timepoint.
Time frame: Day 10, Weeks 3, 6, 9, and 12
Change from baseline in heavy use of rescue analgesic medications.
Changes from baseline at each time point will be classified as improved (yes-to-no), unchanged (no-to-no or yes-to-yes), or worsened (no-to-yes) where "heavy use" is defined as \> 3000 mg acetaminophen \> 3 days/week and/or \> 5 mg oxycodone \> 3 days/week during the 7 days before the given study visit.
Time frame: Day 10, Weeks 3, 6, 9, and 12
Patient Global Impression of Change (PGI-C) in CRPS-related health.
Assessed using a categorical scale of: "very much improved," "much improved," "minimally improved," "no change," "minimally worse," "much worse," and "very much worse," which will be mapped to numeric values of 1, 2, 3, 4, 5, 6, and 7, respectively.
Time frame: Days 4, 7, 10, Weeks 3, and 6
Clinician Global Impression of Change (CGI-C) in CRPS-related health.
Assessed using a categorical scale of: "very much improved," "much improved," "minimally improved," "no change," "minimally worse," "much worse," and "very much worse," which correspond to numeric values of 1, 2, 3, 4, 5, 6, and 7, respectively.
Time frame: Days 4, 7, 10, Weeks 3, 6, and 12
Change from baseline in Patient Global Impression of Severity (PGI-S) in CRPS Severity.
Assessed using a categorical scale of: "none," "minimal," "mild," "moderate," "severe," and "very severe," which will be mapped to numeric values of 0, 1, 2, 3, 4, and 5, respectively.
Time frame: Days 4, 7, 10, Weeks 3, 6, and 12
Change from baseline in Short Form McGill Pain Questionnaire (SF-MPQ) (a) Total Pain Score, (b) each of 4 domain scores, (c) single items.
Assessed using a response to 22 descriptors rated on an 11-point numerical scale (NRS), capturing both neuropathic and non-neuropathic aspects. These descriptors are grouped into four core domains-Continuous Pain, Intermittent Pain, Neuropathic Pain, and Affective Descriptors-with domain scores calculated as the mean of items within each domain. The overall pain score is derived from the average of the 22 items. The complete scale runs from 0 to 10, where a higher score represents greater pain severity.
Time frame: Days 4, 7, 10, and Weeks 3, 6, and 12
Moderate (at least 30%) and substantial (at least 50%) improvement in Short Form McGill Pain Questionnaire (SF-MPQ) (a) Total Pain Score, and (b) each of 4 domain scores.
Assessed using a response to 22 descriptors rated on an 11-point numerical scale (NRS), capturing both neuropathic and non-neuropathic aspects. These descriptors are grouped into four core domains-Continuous Pain, Intermittent Pain, Neuropathic Pain, and Affective Descriptors-with domain scores calculated as the mean of items within each domain. The overall pain score is derived from the average of the 22 items. The complete scale runs from 0 to 10, where a higher score represents greater pain severity.
Time frame: Days 4, 7, 10, Weeks 3, 6, and 12
Change from baseline in the Short Form 36 (SF-36) Item Health Survey (a) 8 domain scores and (b) 2 component summary scores.
Assessment focuses on changes across eight domains: Physical Functioning, Role Limitations due to Physical Health, Role Limitations due to Emotional Problems, Energy/Fatigue, Emotional Well-being, and Social Functioning. Two summary scores-Physical Component Summary and Mental Component Summary-are derived. All domain scores are standardized to a 0-100 scale, with higher scores reflecting better health status
Time frame: Day 10, Weeks 3, 6
Moderate (≥ 30%) and substantial (≥ 50%) improvement in the Short Form 36 (SF-36) Item Health Survey (a) 8 domain scores and (b) 2 component summary scores.
Assessment focuses on changes across eight domains: Physical Functioning, Role Limitations due to Physical Health, Role Limitations due to Emotional Problems, Energy/Fatigue, Emotional Well-being, and Social Functioning. Two summary scores-Physical Component Summary and Mental Component Summary-are derived. All domain scores are standardized to a 0-100 scale, with higher scores reflecting better health status
Time frame: Days 4, 7, 10, Weeks 3, 6, and 12
Change from baseline in the daily sleep interference scale (DSIS).
Assessed using the 7-day average score on the 11-point Numerical Rating Scale (NRS), where 0 represents did not interfere with sleep and 10 represents completely interfered with sleep - unable to sleep due to CRPS pain.
Time frame: Day 10, Weeks 3, 6, 9, and 12
Moderate (≥ 30%) and substantial (≥ 50%) improvement in the daily sleep interference scale (DSIS).
Assessed using the 7-day average score on the 11-point Numerical Rating Scale (NRS), where 0 represents did not interfere with sleep and 10 represents completely interfered with sleep - unable to sleep due to CRPS pain.
Time frame: Day 10, Weeks 3, 6, 9, and 12
Time to moderate (≥ 30%) and substantial (≥ 50%) reduction from baseline in the daily sleep interference scale (DSIS).
Assessed using the 7-day average score on the 11-point Numerical Rating Scale (NRS), where 0 represents did not interfere with sleep and 10 represents completely interfered with sleep - unable to sleep due to CRPS pain.
Time frame: 7-day average
Plan to share: Undecided
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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Studies of the drug tested here: Neridronic acid
Reflex Sympathetic Dystrophy →
Ambros Therapeutics, Inc.