Cladribine (Leustatin) — Clinical FAQs

Q: Is Cladribine safe during pregnancy?

Cladribine pregnancy safety: Category D — causes fetal harm. Cladribine is embryotoxic, fetotoxic, and teratogenic in animals at doses comparable to the human therapeutic range. Effective contraception is required during therapy and for at least 6 months after the final dose in females; males with female partners of reproductive potential should also use contraception. Breastfeeding is contraindicated during and for 1 week after the final infusion.. Oncologists should review the complete prescribing information and discuss reproductive risks with patients before initiating therapy.

Question 1

What is Cladribine FDA-approved to treat?

Accepted Answer

Cladribine is FDA-approved for the following oncology indications: 1. Active hairy cell leukemia (HCL) defined by clinically significant anemia, neutropenia, thrombocytopenia, or disease-related symptoms — a single 7-day continuous IV infusion achieves complete response in approximately 85–90% of treatment-naïve patients, with durable remissions exceeding 10 years in the majority (Leustatin; FDA approved 1993).

Question 2

How does Cladribine work (mechanism of action)?

Accepted Answer

Cladribine (2-chlorodeoxyadenosine; 2-CdA) is a purine nucleoside analog selectively cytotoxic to lymphoid and monocytic cells due to their high ratio of deoxycytidine kinase (DCK) to 5'-nucleotidase activity. After cellular uptake, cladribine is phosphorylated by DCK to its active triphosphate form (CdATP), which accumulates preferentially in lymphocytes and monocytes. CdATP incorporates into DNA, causing strand breaks and inhibiting DNA polymerase and DNA repair enzymes, and activates the intrinsic apoptotic pathway via cytochrome c release and caspase activation. Critically, unlike most antimetabolites, cladribine is cytotoxic to both actively dividing and resting (non-proliferating) lymphocytes — inducing apoptosis independent of S-phase DNA replication. This cell-cycle non-specific activity accounts for its remarkable efficacy in indolent lymphoid malignancies with low proliferative fractions, most notably hairy cell leukemia.

Question 3

How is Cladribine administered?

Accepted Answer

Cladribine is administered Intravenous (IV) or Subcutaneous (SC). Hairy cell leukemia (Leustatin): 0.

Question 4

What are the most common side effects of Cladribine?

Accepted Answer

The most commonly reported side effects of Cladribine (≥10% incidence) include: Fever (69%) — during infusion week (drug fever) and at weeks 2–4 (infection-related; both are common), Fatigue (45%), Rash (27%), Nausea (28%), Headache (22%) and others (14 total). Consult your oncologist for complete prescribing information.

Question 5

Does Cladribine have a black box warning?

Accepted Answer

Yes. Cladribine carries FDA black box warning(s) regarding: 1. Myelosuppression: cladribine causes severe and prolonged myelosuppression. Severe neutropenia (ANC <500/mm³) occurs in the majority of patients during the nadir period (weeks 2–4). Severe thrombocytopenia and anemia also occur, placing patients at high risk for serious and opportunistic infections. Monitor CBC closely and provide appropriate growth factor support, transfusions, and antimicrobial prophylaxis. 2. Neurotoxicity: at high doses used in bone marrow transplant conditioning (substantially higher than standard oncologic doses), cladribine has caused severe and irreversible neurological toxicity including paraparesis and quadriparesis. Severe motor neurotoxicity is rare at standard oncologic doses. 3. Nephrotoxicity: severe and irreversible renal insufficiency has been reported at high doses. Monitor renal function at standard doses, particularly in patients with pre-existing renal impairment or concomitant nephrotoxic agents.

Question 6

Is Cladribine safe during pregnancy?

Accepted Answer

Cladribine pregnancy safety: Category D — causes fetal harm. Cladribine is embryotoxic, fetotoxic, and teratogenic in animals at doses comparable to the human therapeutic range. Effective contraception is required during therapy and for at least 6 months after the final dose in females; males with female partners of reproductive potential should also use contraception. Breastfeeding is contraindicated during and for 1 week after the final infusion.. Oncologists should review the complete prescribing information and discuss reproductive risks with patients before initiating therapy.

Cladribine — Drug Monograph

Mechanism of Action

FDA Indications

Common Side Effects

Clinical Pearl

Related Therapies & Mechanisms