A Proof of Concept Study for a 12 Month Treatment in Patients With C3 Glomerulopathy (C3G) or Immune-Complex Membranoproliferative Glomerulonephritis (IC-MPGN)

Key Inclusion Criteria:

1. 17 to 65 years of age

2. Completion of the ACH471-201 clinical study OR diagnosed with biopsy-confirmed primary
C3G or IC-MPGN at least 3 months prior to the first dose of study drug, prior to 55
years of and not secondary to another underlying condition

3. No more than 50% fibrosis and no more than 50% of glomeruli with cellular crescents on
renal biopsy

4. Clinical evidence of ongoing disease based on at least one of the following findings
attributable to C3G disease or IC-MPGN: significant proteinuria, defined as ≥1 g/day
of protein in a 24-hour urine OR an abnormal eGFR, defined as ≤75 mL/min/1.73 m2 (
CKD-EPI equation for patients > 19 years old; "Bedside Schwartz" equation for patients
<19 years old).

5. On a stable dose of anti-hypertensive medication, anti-proteinuric medications or
mycophenolate mofetil (MMF) for at least 4 weeks prior to the first screening visit

6. Female participants must use highly effective birth control to prevent pregnancy
during the clinical trial and for 30 days after the last dose of study medication

7. Male participants must use highly effective birth control with a female partner to
prevent pregnancy during the clinical trial and for 90 days after the last dose of
study medication

8. Must be up-to-date on routine vaccinations, or willing to be brought up-to-date, based
on local guidelines

9. Must be willing, at all times for the duration of study participation, to have
transportation and telephone access, and to be within one hour of an emergency medical
center

Key Exclusion Criteria

1. Have a history of a major organ transplant (e.g., heart, lung, kidney, liver) or
hematopoietic stem cell/marrow transplant

2. Have an estimated GFR <30 mL/min/1.73 m2 at the time of screening or at any time over
the preceding four weeks

3. Is receiving renal replacement therapy

4. Have evidence of monoclonal gammopathy of unclear significance(MGUS), infections,
malignancy, autoimmune diseases, or other conditions to which C3G or IC-MPGN may be
secondary

5. Have a history of febrile illness, a body temperature >38°C, or other evidence of a
clinically significant active infection, within 14 days prior to ACH-0144471
administration

6. Positive serology for human immunodeficiency virus, hepatitis B infection, or
hepatitis C infection

7. Have a history of meningococcal infection, or a first-degree relative or household
contact with a history of meningococcal infection

8. . Have received eculizumab at any dose or interval within the past 75 days prior to
the first dose of ACH-0144471

9. Have received tacrolimus or cyclosporine within 2 weeks of the first dose of
ACH-0144471

10. Have received blood or blood products, or undergone plasmapheresis or plasma exchange,
within 30 days of screening

NOTE: Additional inclusion/exclusion criteria will apply, per protocol