LTS15823 (long-term extension of the EFC15392 study) was stopped after protocol specified interim analysis for futility of the parent EFC15392 study met the prespecified stopping rule based on the primary outcome measure.

Primary Objective:

-To determine the effect of early versus delayed treatment with venglustat on the total kidney volume (TKV) in participants at risk of rapidly progressive autosomal dominant polycystic kidney disease (ADPKD).

Secondary Objective:

• To determine the effect of early versus delayed treatment with venglustat on the renal function (estimated glomerular filtration rate [eGFR] [Chronic Kidney Disease Epidemiology Collaboration {CKD-EPI} equation]).
• To characterize the safety profile of venglustat.
• To evaluate the effect of venglustat on the lens by ophthalmological examination.
• To evaluate the effect of venglustat on mood using Beck Depression Inventory-II (BDI-II).

The planned study duration per participant was 25.5 months (maximal). Screening period (when applicable): up to 2 weeks. Core treatment period: 24 months. Follow-up: 30 days after final dose of the investigational medicinal product (IMP) (venglustat).

Inclusion criteria :

• Male or female adult with ADPKD who had completed the treatment period in Stage 1 or Stage 2 of Study EFC15392 (NCT03523728).

• The participants who had an eGFR >30 mL/min/1.73 m^2:

  1. Measured at Visit 11 of the EFC15392 study for participant enrolled in the LTS15823 study at the time of Visit 12 (Month 24; end-of treatment visit) of the EFC15392 study.
  2. Measured at Screening visit for participant enrolled in the LTS15823 study not concomitantly to the Visit 12 (Month 24; end-of treatment visit) of the EFC15392 study.

• Contraceptive used by men and women should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies.

  1. Male participants who agreed to practice true abstinence in line with their preferred and usual lifestyle or to use double-contraceptive methods for the entire duration of the study and for at least 90 days following their last dose of IMP.
  2. Female participants who had a negative urine pregnancy test at the Baseline visit and agreed to practice true abstinence in line with their preferred and usual lifestyle or to use double contraceptive methods (including a highly effective method of contraception) for the entire duration of the study and for at least 6 weeks following their last dose of IMP.

• Capable of giving signed informed consent before performance of any study related procedures not part of standard medical care.

• Able to read, comprehend, and respond to the study questionnaires.

Exclusion criteria:

• For participants who had lag phase between the end of the EFC15392 study and Screening visit (Visit 0) in the LTS15823 study.
• The participant had a new clinically significant, uncontrolled medical condition that, in the opinion of the Investigator, would put the safety of the participant at risk through participation, or which would affect the efficacy or safety analysis if the condition exacerbated during the study, or that might significantly interfere with study compliance, including all prescribed evaluations and follow-up activities.
• A history of drug abuse and/or alcohol abuse or alcohol dependence during the lag phase between the end of the EFC15392 study and Screening visit (Visit 0) in the LTS15823 study when applicable.
• Administration of tolvaptan or other polycystic kidney disease-modifying agents (somatostatin analogues) within 3 months prior to the Screening visit (Visit 0) in the LTS15823 study when applicable.
• The participant was currently receiving potentially cataractogenic medications, including a chronic regimen (more frequently than every 2 weeks) of any route of corticosteroids (including medium and high potency topical steroids), or any medication that may cause cataract, according to the Prescribing Information.
• The participant had received strong or moderate inducers or inhibitors of CYP3A4 within 14 days or 5 half lives, whichever was longer, prior to the Baseline visit (including consumption of grapefruit-containing products within 72 hours of starting venglustat administration).
• Participation in another investigational interventional study or use of IMP, within 3 months or 5 half-lives, whichever was longer, before the Baseline visit (Visit 1) except participation in the EFC15392 study when applicable.
• Liver enzymes (alanine aminotransferase /aspartate aminotransferase) or total bilirubin >2 times the upper limit of normal unless the participant had the diagnosis of Gilbert syndrome. Participants with the Gilbert syndrome should had no additional symptoms or signs which suggest hepatobiliary disease and serum total bilirubin level no more than 3 milligrams per decilitre (mg/dL) (51 micromoles per litre [μmol/L]) with conjugated bilirubin less than 20 percent (%) of the total bilirubin fraction.

For participants with or without lag phase between the end of EFC15392 study and entry into LTS15823 study:

• The participant was pregnant or lactating.
• Presence of severe depression as measured by BDI-II >28 at Visit 1 (for participants enrolled in the LTS15823 study at the time of the end of treatment visit of the EFC15392 study) or at Visit 0 (for participants enrolled in the LTS15823 study after the end-of-treatment visit of the EFC15392 study).
• Sensitivity to any of the study interventions, or components thereof, or drug or other allergy that, in the opinion of the Investigator, contraindicates participation in the study.

The above information was not intended to contain all considerations relevant to a participant's potential participation in a clinical trial.

Qualified researchers may request access to patient level data and related study documents including the clinical study report, study protocol with any amendments, blank case report form, statistical analysis plan, and dataset specifications. Patient level data will be anonymized and study documents will be redacted to protect the privacy of trial participants. Further details on Sanofi's data sharing criteria, eligible studies, and process for requesting access can be found at: https://vivli.org

Analysis was performed on enrolled population which included all participants allocated to an intervention kit by interactive response technology (IRT) regardless of whether the intervention was received or not.

From the first administration of the IMP in LTS15823 study up to the last IMP administration in LTS15823 study + 30 days (i.e., up to approximately 20 weeks)

Reported AEs were TEAEs i.e., AEs that developed/worsened during the 'TEAE period'. Analysis was performed on long-term extension safety population.

The study was terminated prematurely by the Sponsor following a decision to terminate the parent study EFC15392. Termination decision was due to lack of efficacy in ADPKD population and not linked to safety findings with venglustat.