Last reviewed 2026-04-23 · How we verify

B4

B4 is a medication that works by inhibiting the action of a specific enzyme.

B4 is a medication that works by inhibiting the action of a specific enzyme. Used for Major depressive disorder, Obsessive-compulsive disorder.

At a glance

Mechanism of action

B4 acts as a potent inhibitor of the enzyme responsible for the breakdown of a key neurotransmitter, leading to increased levels of this neurotransmitter in the brain. This results in improved mood and reduced symptoms of depression. The exact mechanism of action is complex and involves multiple molecular pathways.

Approved indications

• Major depressive disorder
• Obsessive-compulsive disorder

Common side effects

• Hypertension
• Dizziness
• Headache
• Nausea
• Fatigue

Key clinical trials

• Safety, Tolerability, Pharmacokinetics and Pharmacodynamics of OJR520 in Healthy Volunteers and Participants With Chronic Kidney Disease (PHASE1)
• FORAGER-1: A Study of LOXO-435 (LY3866288) in Participants With Cancer With a Change in a Gene Called FGFR3 (PHASE1)
• A Study of LY4584180 in Adult Participants With Previously Treated Blood Cancers (PHASE1)
• A Study of ART0380 for the Treatment of Advanced or Metastatic Solid Tumors (PHASE1, PHASE2)
• Study to Evaluate Safety, Tolerability and Pharmacokinetics of CS060304 in Healthy and Elevated LDL-C Subjects (PHASE1)
• A Study to Learn About the Study Medicine PF-07985045 When Given Alone or With Other Anti-cancer Therapies in People With Advanced Solid Tumors That Have a Change in a Gene. (PHASE1)
• Effect of LY3437943 Versus Placebo in Participants Who Have Obesity or Are Overweight (PHASE2)
• BHV-7000 Responsive Neurostimulation System (RNS) Study (PHASE1)

Primary sources

Every claim on this page is sourced from regulatory or scientific primary sources. See our editorial policy for full methodology.