Study on Efficacy and Safety of LNP023 in C3 Glomerulopathy Patients Transplanted and Not Transplanted

Inclusion Criteria for Cohort A and B: * Written informed consent must be obtained before any assessment is performed * Male and female patients between the ages of 18 to 65 (inclusive) at screening * C3G patients wit proteinuria * Able to communicate well with the investigator, to understand and comply with the requirements of the study * At screening and baseline visits, patients must weigh at least 35 kg * Supine vital signs should be within the following ranges : oral body temperature between 35.0-37.5 °C systolic blood pressure, 80-170 mm Hg diastolic blood pressure, 50-105 mm Hg pulse rate, 45 - 100 bpm . Inclusion Criteria for Cohort A: * Estimated GFR (using the CKD-EPI formula) or measured GFR ≥30 mL/min per 1.73 m2 for patients on a maximum recommended or maximum tolerated dose of an angiotensin converting enzyme inhibitor (ACEI) or angiotensin receptor blocker (ARB) * UPCR ≥ 100 mg/mmol (equivalent to ≥ 1 g/24h total urinary protein excretion) * Prior to entry, all patients must have been on supportive care including a maximally tolerated dose of ACEi or ARB for at least 30 days. Inclusion Criteria for Cohort B: * No histological/laboratory/clinical signs of allorejection * If applicable, induction treatment after allotransplantation needs to be completed \>30 days before inclusion. * Transplantation of a kidney allograft \>90 days before inclusion * Patients need to be on a stable dose of immunosuppressive regimen prior to inclusion. Any approved treatments are allowed for this purpose. Exclusion Criteria for Cohort A and B: * Use of other investigational drugs at the time of enrollment, or within 5 half-lives of randomization, or within 30 days, whichever is longer; or longer if required by local regulations * A history of clinically significant ECG abnormalities, * Known family history or known presence of long QT syndrome or Torsades de Pointes * Use of agents known to prolong the QT interval unless they can be permanently discontinued for the duration of the study * Pregnant or nursing (lactating) women, where pregnancy is defined as the state of a female after conception and until the termination of gestation, confirmed by a positive hCG laboratory test. * Women of child bearing potential, defined as all women physiologically capable of becoming pregnant, unless they are using highly effective methods of contraception during dosing and for 1 week after stopping of investigational drug. * History of immunodeficiency diseases, or a positive HIV test result. * Chronic infection with Hepatitis B (HBV) or Hepatitis C (HCV). * Patients who cannot receive vaccinations against N. meningitidis, S. pneumoniae, or H. influenzae