Last reviewed 2026-04-20 · How we verify

Leustatin (CLADRIBINE)

Leustatin works by inhibiting the enzyme that breaks down cyclic adenosine monophosphate (cAMP), leading to an accumulation of cAMP and subsequent activation of various cellular pathways.

Leustatin (Cladribine) is a small molecule purine antimetabolite that targets cAMP-specific 3',5'-cyclic phosphodiesterase 4A. It was originally developed and is currently owned by Janssen Pharmaceuticals. Leustatin is FDA-approved for the treatment of hairy cell leukemia and relapsing-remitting multiple sclerosis. The drug is off-patent, with multiple generic manufacturers available. Key safety considerations include its potential for bone marrow suppression and secondary malignancies.

At a glance

Mechanism of action

The mechanism by which cladribine exerts its therapeutic effects in patients with multiple sclerosis has not been fully elucidated but is thought to involve cytotoxic effects on and lymphocytes through impairment of DNA synthesis, resulting in depletion of lymphocytes.

Approved indications

• Hairy cell leukemia
• Relapsing remitting multiple sclerosis

Boxed warnings

• WARNING: MALIGNANCIES AND RISK OF TERATOGENICITY Malignancies Treatment with cladribine tablets may increase the risk of malignancy. Cladribine tablets are contraindicated in patients with current malignancy. In patients with prior malignancy or with increased risk of malignancy, evaluate the benefits and risks of the use of cladribine tablets on an individual patient basis. Follow standard cancer screening guidelines in patients treated with cladribine tablets [see Contraindications (4) and Warnings and Precautions ( 5.1 )] . Risk of Teratogenicity Cladribine tablets are contraindicated for use in pregnant women and in women and men of reproductive potential who do not plan to use effective contraception because of the potential for fetal harm. Malformations and embryolethality occurred in animals. Exclude pregnancy before the start of treatment with cladribine tablets in females of reproductive potential. Advise females and males of reproductive potential to use effective contraception during cladribine tablets dosing and for 6 months after the last dose in each treatment course. Stop cladribine tablets if the patient becomes pregnant [see Contraindications (4), Warnings and Precautions (5.2), and Use in Specific Populations (8.1, 8.3)] . WARNING: MALIGNANCIES and RISK OF TERATOGENICITY See full prescribing information for complete boxed warning. Malignancies Cladribine tablets may increase the risk of malignancy. Cladribine tablets are contraindicated in patients with current malignancy; evaluate the benefits and risks on an individual basis for patients with prior or increased risk of malignancy. ( 5.1 ) Risk of Teratogenicity Cladribine tablets are contraindicated for use in pregnant women and in women and men of reproductive potential who do not plan to use effective contraception because of the risk of fetal harm. ( 5.2 )

Common side effects

• Neutropenia
• Fever
• Infection
• Anemia
• Thrombocytopenia
• Fatigue
• Malaise
• Pyrexia
• Nausea
• Vomiting
• Dyspnea
• Rash

Key clinical trials

• Testing the Combination of Anti-cancer Drugs, Tovorafenib Plus Rituximab, in Patients With Hairy Cell Leukemia (PHASE1,PHASE2)
• Efficacy and Safety of a New Formulation of Oral Cladribine Compared With Placebo in Participants With Generalized Myasthenia Gravis (MyClad) (PHASE3)
• A Study of Vemurafenib and Obinutuzumab Compared to Cladribine and Rituximab in People With Hairy Cell Leukemia (HCL) (PHASE2)
• Consolidation Therapy With Cladribine in Relapsing Multiple Sclerosis Patients
• IMPACT-AML: A Randomized Pragmatic Clinical Trial for Relapsed or Refractory Acute Myeloid Leukemia. (PHASE3)
• A Phase 1, Open-Label, Sequential Cross-over, Bioavailability/Bioequivalence Study to Compare the Pharmacokinetics of Oral Cladribine With the Reference Listed Drug, Intravenous Cladribine (PHASE1)
• CLAG-M or FLAG-Ida Chemotherapy and Reduced-Intensity Conditioning Donor Stem Cell Transplant for the Treatment of Relapsed or Refractory Acute Myeloid Leukemia, Myelodysplastic Syndrome, or Chronic Myelomonocytic Leukemia (PHASE1)
• A Phase 1b/2 Open-label, Dose-ranging Safety and Efficacy Study of Oral Cladribine in Patients With Acute Myeloid Leukemia (AML) (PHASE1,PHASE2)

Patents

Primary sources

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Competitive intelligence

For the full competitive landscape — auto-detected comparators, recent regulatory actions across the set, upcoming PDUFA, patent timeline, sponsor landscape:

• Leustatin CI brief — competitive landscape report
• Leustatin updates RSS · CI watch RSS