A First in Human, Dose Escalation Study to Evaluate the Safety and Tolerability of BBP-671 in Healthy Volunteers and Patients With Propionic Acidemia or Methylmalonic Acidemia

Inclusion Criteria (Healthy Volunteers): * Subject is male or female 18 to 55 yrs old * Subject has a BMI 18 to 32 kg/m\^2 * Female and male subjects must use effective method of birth control * Female subjects must have negative pregnancy test prior to first dose of study drug * Subject must not have any clinically significant history or presence of ECG findings * Subject must be in good general health Inclusion Criteria (PA or MMA Patients): * Patient is male or female 15 to 55 yrs old * Patient has a BMI 18 to 32 kg/m\^2 * Female and male patients must use effective method of birth control * Female patients must have negative pregnancy test prior to first dose of study drug * Patient must have confirmed PA or MMA diagnosis * Patient with MMA must have elevated plasma MMA levels * Patient is willing to provide access to medical records for the last 6-12 months of care prior to study initiation * Patient is on consistent disease management and treatment regimen is stable for at least 30 days prior to study initiation. Exclusion Criteria (Healthy Volunteers): * Subject has used prescription drugs (contraceptive medications are allowed) within 4 weeks before first dose of study drug or over-the-counter medication within 7 days of the first dose of study drug * Subject who is unable or unwilling to refrain from wearing contact lenses during participation in the study. * Subject has a history of dry eye or eye surgery, including radial keratotomy and LASIK surgery. * Subject who has taken the COVID-19 vaccine, the last vaccine dose must be at least 14 days prior to first dose of study drug. * Subject has abnormal laboratory test results * Subject has a baseline eGFR \<90 mL/minute * Subject has positive result for Hepatitis B, Hepatitis C, or HIV * Female subject is non-pregnant and non-lactating * Subject is a smoker or has used nicotine or nicotine-containing products * Subject has a history of alcohol or drug abuse within 12 months prior to first dose of study drug and/or has a positive result prior to dosing or throughout the study * Subject has donated blood or blood products \>450mL within 30 days prior to study drug dosing * Subject has a history of relevant drug or food allergies * Subject has received study drug in another investigational study within 30 days of dosing * Subject has undergone prior liver and/ or kidney transplant. Exclusion Criteria (PA or MMA Patients): * Patient has used prescription drugs (contraceptive medications are allowed) within 4 weeks before first dose of study drug or over-the-counter medication within 7 days of the first dose of study drug that is not part of their PA or MMA disease management and treatment * Patient who has taken the COVID-19 vaccine, the last vaccine dose (or booster) must be at least 14 days prior to first dose of study drug. * Patient is unable or unwilling to refrain from wearing contact lenses during participation in the study. * Patient has a history of dry eye or eye surgery, including radial keratotomy and LASIK surgery. * Patient has clinically significant abnormal laboratory test results unrelated to PA or MMA * Patient has a baseline eGFR \<60 mL/minute * Patient has positive result for Hepatitis B, Hepatitis C, or HIV * Female patient is non-pregnant and non-lactating * Patient has a history of alcohol or drug abuse within 12 months prior to first dose of study drug and/or has a positive result prior to dosing or throughout the study * Patient has donated blood or blood products \>450mL within 30 days prior to study drug dosing * Patient has a history of relevant drug or food allergies * Patient has received study drug in another investigational study within 30 days of dosing * PA patient has undergone prior liver and/ or kidney transplant. Prior liver and/or kidney transplant is allowed for patients with MMA. * Patient has had a recent infection requiring system antibiotics within 4 weeks of Baseline or any active infection that precludes the patient from participation * Patient has Grade 3 or 4 heart failure according to the Modified Ross Heart Failure Classification for Children or the New York Heart Association. * Patient has been exposed to gene therapy for PA or MMA at any time prior to study entry. * Patient is currently taking sensitive CYP3A4 substrates (e.g., tacrolimus or sirolimus)