This is an open-label extension study of IMR-687 in adult patients who completed Imara's blinded Phase 2a study (IMR-SCD-102). The open-label extension study will evaluate long-term safety and tolerability.

This is an open-label extension study of IMR-687 in adult patients with SCA who were previously participants in the Phase 2a study titled "A Phase 2a, Randomised, Double-Blind, Placebo-Controlled Study of IMR-687 in Adult Patients with Sickle Cell Anaemia (Homozygous HbSS or Sickle-β0 Thalassemia)."

This open-label extension study with IMR-687 will evaluate the long-term safety and tolerability of IMR 687 in adult SCA patients. Exploratory long-term PD parameters will also be examined.

Inclusion Criteria:

1. Completed Study IMR-SCD-102.
2. Female subjects must not be pregnant, not be breast feeding, and be highly unlikely to become pregnant. Male subjects must be unlikely to impregnate a partner.
3. Subjects must be capable of giving informed consent and reading and signing the informed consent form after the nature of the study has been fully explained to them
4. Subjects must be willing and able to complete all study assessments and procedures and to communicate effectively with the investigator and site staff.

Exclusion Criteria:

1. Subjects with Hb >12.5 g/dL or <6 g/dL
2. Subjects with known active hepatitis B or hepatitis C, with active or acute event of malaria or who are known to be positive for human immunodeficiency virus (HIV)
3. eGFR <50 mL/min
4. AST/ALT > 3x the upper limit of normal