Calciphylaxis is a rare but serious condition that leads to painful skin lesions. At present, there is no approved treatment for calciphylaxis. This research study is planned to examine the potential benefits of a new treatment (EPN-701) in patients with calciphylaxis. The present early clinical study will also evaluate the pharmacology of EPN-701 and whether it can be safely used in patients with calciphylaxis. Findings will inform the planning of a future definitive study to establish EPN-701 as an approved treatment for calciphylaxis.

This is a phase 2 double-blind RCT that will randomly assign 60 adult dialysis-dependent patients with calciphylaxis to either EPN-701 (10 mg/day administered orally) or a matched placebo in a 1:1 ratio for 24 weeks. Standardized background clinical care will be applied to all participants.

Primary objective will be to determine the clinical efficacy and safety of EPN-701 in dialysis-dependent patients with calciphylaxis. The clinical efficacy will be assessed by pre-post (Baseline-Week 24) change in pain intensity and calciphylaxis wound surface area.

Secondary objective will be to examine the safety of EPN-701 in dialysis-dependent patients with calciphylaxis. Safety will be assessed by active monitoring for adverse events throughout the trial period.

The pharmacodynamic efficacy will be primarily assessed by pre-post (Baseline-Week 12) change in plasma ucMGP among the trial arms. EPN-701 plasma concentration time profiles and other pharmacokinetic assessments will also be assessed.

Exploratory outcomes will be pre-post (Baseline-Week 24) changes in radiotracer uptake indicative of calcification burden, wound severity scores, hospitalization, mortality, and quality of life. The Investigators will also explore novel biomarkers of calciphylaxis via plasma proteomics and examine the associations between changes in ucMGP, radiotracer uptake, and novel biomarkers with patient-oriented clinical outcomes to inform the selection of efficacy endpoints for a future phase 3 RCT.

Findings from the proposed trial will inform the end point selection and design of a future phase 3 trial aimed at establishing a targeted novel therapy for calciphylaxis.

Inclusion Criteria:

1. Participant must provide written or electronic consent after the nature of the study has been explained, and prior to any research-related procedures, per the International Conference on Harmonization (ICH) Good Clinical Practice (GCP)
2. Clinical diagnosis of calciphylaxis confirmed by the Investigator with presence of at least one ulcerated skin lesion and moderate or severe pain (worst pain intensity in the preceding 24 hours of at least 5 on a 0-10 scale). Consistent with the clinical practice and expert recommendations, histological confirmation of calciphylaxis diagnosis by a skin biopsy is not a requirement for participation.
3. ESKD requiring thrice weekly hemodialysis
4. Male or female aged ≥18 years
5. Women of childbearing potential (WOCBP) as defined in Clinical Trials Facilitation and Coordination Group (CTFG, 2020) must have a negative serum pregnancy test (defined as serum hCG ≤25 mIU/mL [Haninger-Vacariu, 2020]) at Screening
6. Women of childbearing potential (WOCBP) must be using or agree to use one highly effective form of contraception and a barrier method from Screening through 30 days after the last dose of study treatment. See Appendix C for further information about highly effective forms of contraception.
7. Males who are sexually active must agree to use condoms from the period following first dose of study treatment through four weeks after the last dose of study treatment. Males with a WOCBP partner must agree to use one highly effective form of contraception in addition to condoms from Screening through 30 days after the last dose of study treatment.
8. Males must agree to not donate sperm from the period following the first dose of study treatment through 4 weeks after last dose of study treatment. WOCBP who are participants or partners of fertile male participants must agree not to donate ova from the period following the first dose of study treatment through 4 weeks after last dose of study treatment.

Exclusion Criteria:

1. In the opinion of the Investigator, presence of any clinically significant disease outside of calciphylaxis that may impact study participation and/or confound interpretation of the study results
2. Hospitalized at the time of Screening. Patients discharged from a hospital admission ≥24 hours prior to Screening may be eligible for participation.
3. Septic shock
4. Hospice or comfort care including withdrawal from dialysis
5. Malignancy within the last year, except non-melanoma skin cancers, cervical carcinoma in situ, or localized prostate cancer.
6. Concurrent participation in another interventional clinical study and/or receipt of any other investigational new drug within four weeks prior to the first dose of study treatment, or use of an investigational device, through completion of participation in the study
7. Previous participation in a study of EPN-701
8. Participants who are pregnant, trying to become pregnant, or breastfeeding
9. Participants who are trying to father a child
10. Peritoneal dialysis participants
11. Kidney transplant recipients who are receiving immunosuppression at the time of Screening and patients who have an imminent transplant plan. Patients who have received a kidney transplant that has failed, necessitating dialysis, and who are no longer on immunosuppression may participate.
12. History of or current diagnosis of cirrhosis
13. Current use of prohibited medications, including vitamin K-containing medications and warfarin. Patients who have discontinued warfarin treatment upon the diagnosis of calciphylaxis will be eligible for Screening.