A Study to Evaluate the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of PRO-203 in Healthy Volunteers and Participants With Systemic Sclerosis

NCT07641634 | Recruiting Phase 1

• 1 other identifier: PRO-203-101
• Study Type: interventional
• Target: 74
• Locations: 2 countries
• Sites: 2

Brief Summary

The purpose of this study is to determine the safety, tolerability, pharmacokinetics, and pharmacodynamics of PRO-203 in healthy volunteers and participants with systemic sclerosis. Participants will be given PRO-203 under the skin (i.e., subcutaneously).

Conditions

Healthy Volunteers; Systemic Sclerosis (SSc); Scleroderma, Systemic; Scleroderma

Keywords

Systemic sclerosis; SSc; Scleroderma; B cell depletion

Outcome Measures

Primary Outcomes (9)

• Number of participants with treatment-emergent adverse events (TEAEs)

  TEAEs graded by type and frequency per NCI CTCAE v5.0. Applies to Part 1 (Healthy Volunteers) and Part 2 Main Study (Systemic Sclerosis).

  From time of first dose through week 13.

• Number of participants with treatment-emergent serious adverse events (TESAEs).

  TESAEs graded by type and frequency per NCI CTCAE v5.0. Applies to Part 1 (Healthy Volunteers) and Part 2 Main Study (Systemic Sclerosis).

  From time of first dose through Week 13

• Number of participants with dose-limiting toxicities (DLTs)

  DLT defined per protocol as any related TEAE of NCI CTCAE v5.0. Applies to Part 1 (Healthy Volunteers) and Part 2 Main Study (Systemic Sclerosis).

  From time of first dose through Week 13.

• Number of participants with clinically significant changes in clinical laboratory values

  Clinical significance determined by investigator judgment per NCI CTCAE v5.0. Applies to Part 1 (Healthy Volunteers) and Part 2 Main Study (Systemic Sclerosis).

  From time of first dose through Week 13

• Number of participants with clinically significant changes in 12-lead ECG parameters

  Standard 12-lead ECG parameters such as heart rate, PR interval, QRS duration, QT interval, and corrected QT interval (QTcF). Clinical significance determined by investigator judgment. Applies to Part 1 (Healthy Volunteers) and Part 2 Main Study (Systemic Sclerosis).

  From time of first dose through Week 13

• Number of participants with clinically significant changes in vital signs

  Vital signs can include systolic and diastolic blood pressure, pulse rate, respiratory rate, and temperature. Clinical significance determined by investigator judgment. Applies to Part 1 (Healthy Volunteers) and Part 2 Main Study (Systemic Sclerosis).

  From time of first dose through Week 13

• Number of participants with TEAEs (Part 2 SSc, Long-term Extension)

  Applies to Part 2 (Systemic Sclerosis) Long-term Extension (LTE). Includes TEAEs occurring during LTE. TEAEs graded by type and frequency per NCI CTCAE v5.0.

  From time of first dose through Week 49

• Number of participants with TESAEs (Part 2 SSc, Long-term Extension)

  Applies to Part 2 (Systemic Sclerosis) Long-term Extension (LTE). Includes TESAEs occurring during LTE. TESAEs graded by type and frequency per NCI CTCAE v5.0.

  From time of first dose through Week 49

• Number of participants with clinically significant changes in clinical laboratory values or vital signs (Part 2 SSc, Long-term Extension)

  Applies to Part 2 (Systemic Sclerosis) Long-term Extension (LTE). Clinical significance determined by investigator judgment per NCI CTCAE v5.0.

  From time of first dose through Week 49

Secondary Outcomes (16)

• Maximum Serum Concentration (Cmax) of PRO-203

  From time of first dose through Week 13

• Time to Maximum Serum Concentration (Tmax) of PRO-203

  From time of first dose through Week 13

• Area Under the Serum Concentration-Time Curve (AUC) of PRO-203

  From time of first dose through week 13

• Systemic Clearance of PRO-203

  From time of first dose through week 13

• Elimination Half-Life (t1/2) of PRO-203

  From time of first dose through Week 13

Study Arms (3)

Part 1: PRO-203

EXPERIMENTAL

Healthy participants receive single ascending dose of PRO-203 across 5 sequential cohorts

Drug: PRO-203

Part 1: Placebo

PLACEBO COMPARATOR

Matching SC placebo administered to randomized Part 1 participants

Other: Placebo

Part 2: Multiple Doses of PRO-203

EXPERIMENTAL

Participants with systemic sclerosis receive PRO-203 across a multiple dose regimen across 3 sequential cohorts, including optional retreatment in LTE.

Drug: PRO-203

Interventions

PRO-203 DRUG

PRO-203 administered as escalating single doses in healthy participants or as sequential multiple-dose regimens in participants with systemic sclerosis.

Part 1: PRO-203; Part 2: Multiple Doses of PRO-203

Placebo OTHER

Matching placebo comparator for Part 1 participants.

Part 1: Placebo

Eligibility Criteria

• Age: 18 Years - 65 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Is male or female, age 18 to 65 years, inclusive, at Screening.
• Able to provide Informed Consent.
• Absolute B cell count \> 25 cells/uL.
• In good general health, determined by no clinically significant findings in the of the investigator from medical history, physical examination, 12-lead ECG, clinical laboratory findings, and vital signs at Screening and Day -1 (participants with Gilbert's disease with associated abnormalities of liver function tests are eligible for enrollment).
• Up to date vaccination status per local guidelines (including but not limited to influenza vaccine, COVID booster and hepatitis B vaccine).
• Fulfill 2013 ACR/ EULAR criteria for classification of SSc with a total score of ≥ 9.
• Active disease defined as at least two of the following at screening:
• Disease duration ≤ 2 years (since onset of first-non-Raynaud-symptom), or
• Elevated acute phase reactant levels (CRP ≥ 6 mg/L, erythrocytes sedimentation rate \[ESR\] ≥ 28 mm/1h, or platelet count ≥ 330,000/µL), or
• Baseline mRSS ≥10 with evidence of progression, defined as mRSS increase at least 3 units, or involvement of 1 new body area and mRSS increase at least 2 units, or involvement of 2 new body areas (each within the previous 6 months), or
• ≥ 1 tendon friction rub, or
• Elevation of CK or aldolase \> 2 × the upper limit of normal (ULN) consistent with SSc-related myopathy, or
• Progressive fibrosing interstitial lung disease (ILD) as defined by at least one of the following criteria at any time within the prior 2 years:
• relative decline in forced vital capacity (FVC) % predicted ≥ 10%, or
• relative decline in FVC % predicted ≥ 5% to \<10% and worsened respiratory symptoms, or

You may not qualify if:

• Any clinically significant underlying illness in the opinion of the investigator.
• Active infection within 4 weeks prior to screening. Participants receiving IV antibiotics or having received IV antibiotics within 14 days prior to enrollment are excluded.
• Positive QuantiFERON-Gold TB test at screening.
• Plan to receive live, attenuated vaccine after signing ICF (inactive vaccines, such as the flu vaccine, are allowed).
• Evidence of malignant disease or malignancies diagnosed within the previous 5 years (except for treated local basal or squamous cell carcinoma of the skin or carcinoma in situ of the cervix uteri that had been excised and cured).
• Currently enrolled in another investigational device or drug study, or less than 30 days or 5 half-lives of the prior investigational agent (whichever is longer) have passed since ending another investigational device or drug study or plans to enroll in another investigational device or drug study during the course of this study.
• Social smokers e.g. up to 10 cigarettes per week (or equivalent amounts of nicotine containing products) and willing to abstain during inpatient stay, are allowed
• Use of any prescription medication within 14 days and OTC medications, vitamins, herbal medications (e.g., St. John's wort), or cannabis, except for contraceptive medications and as needed (prn) acetaminophen/paracetamol (not exceeding 2 grams/day) within 7 days prior to administration of the study drug and throughout the study.
• Rheumatic autoimmune disease other than SSc.
• Positive anti-centromere antibodies.
• Pulmonary disease with FVC ≤ 45% of predicted, or DLCO ≤ 35% of predicted.
• Class 2 or higher pulmonary arterial hypertension or evidence of other moderately severe pulmonary disease.
• Renal crisis within 6 months prior to Screening.
• Prior treatment with cellular immunotherapy (eg, CAR-T) or gene therapy product directed at any target.
• Previous treatment with chlorambucil, bone marrow transplantation, or total lymphoid irradiation.

Sponsors & Collaborators

• Prolium Bioscience, Inc: lead

Study Sites (2)

Nucleus Network

Melbourne, Victoria, 3004, Australia

RECRUITING

Nanjing Drum Tower Hospital

Nanjing, China

NOT YET RECRUITING

MeSH Terms

Conditions

Scleroderma, Systemic; Scleroderma, Diffuse

Condition Hierarchy (Ancestors)

Connective Tissue Diseases; Skin and Connective Tissue Diseases; Skin Diseases

Study Officials

• Salim Mujais

  Prolium Bioscience, Inc

  STUDY DIRECTOR

Central Study Contacts

Sergio Rodriguez

CONTACT

(646) 597-6980; info@proliumbio.com

Study Design

• Study Type: interventional
• Phase: phase 1
• Allocation: RANDOMIZED
• Masking: TRIPLE
• Who Masked: PARTICIPANT, INVESTIGATOR, OUTCOMES ASSESSOR
• Masking Details: Double (Participant, Investigator) - Part 1 only; Open Label - Part 2
• Purpose: TREATMENT
• Intervention Model: SEQUENTIAL
• Sponsor Type: INDUSTRY
• Responsible Party: SPONSOR

Model Details: Dose escalation

Study Record Dates

• First Submitted: December 10, 2025
• First Posted: June 11, 2026
• Study Start: October 27, 2025
• Primary Completion (Estimated): January 1, 2027
• Study Completion (Estimated): February 1, 2027
• Last Updated: June 11, 2026

Record last verified: 2026-06

Data Sharing

• IPD Sharing: Will share

Locations

AU (1); CN (1)