Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
EKTERLY vs CLADRIBINE
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Ekterly is a tissue-selective estrogen receptor degrader (SERD) that binds to the estrogen receptor (ER) and induces conformational changes leading to ER degradation. It antagonizes ER-mediated gene transcription and signaling, thereby inhibiting ER-dependent breast cancer cell proliferation.
Cladribine is a purine nucleoside analog that is phosphorylated intracellularly to its active triphosphate form, which inhibits DNA synthesis and repair, leading to cell death, particularly in lymphocytes. It also depletes adenosine deaminase (ADA) and accumulates in cells with high deoxycytidine kinase activity.
Treatment of postmenopausal women with estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced or metastatic breast cancer with disease progression following at least one line of endocrine therapy.
FDA-approved: Treatment of hairy cell leukemia.,Off-label: Chronic lymphocytic leukemia (CLL), multiple sclerosis (relapsing forms), Waldenström macroglobulinemia, cutaneous T-cell lymphoma, and as part of conditioning regimens for hematopoietic stem cell transplantation.
10 mg orally once daily
0.09 mg/kg/day IV over 2 hours for 7 consecutive days; or 0.14 mg/kg/day IV over 2 hours for 5 consecutive days (total dose 0.7 mg/kg per course).
Terminal elimination half-life is 12 hours. Steady state reached within 2 days. Accumulation negligible with once-daily dosing.
Terminal elimination half-life is approximately 5.4 hours (range 4.6–6.7 hours) after intravenous administration; prolonged in renal impairment.
Ekterly is primarily metabolized by CYP3A4 and UGT1A8/1A9, with minor contributions from CYP2C9 and CYP2C19.
Cladribine is primarily metabolized intracellularly by deoxycytidine kinase to its active triphosphate. It is also phosphorylated by deoxyguanosine kinase in mitochondria. Catabolism involves deamination by adenosine deaminase (ADA) to 2-chloroadenine, which is further metabolized.
Renal excretion accounts for 70% of elimination, with 30% hepatobiliary/fecal. Approximately 15% is excreted unchanged in urine; the remainder as glucuronide metabolites.
Renal (approximately 50% as unchanged drug); fecal elimination is minimal (<5%).
92% bound primarily to albumin, with minor binding to alpha-1-acid glycoprotein.
Approximately 20–30% bound to plasma proteins.
Vd is 0.3 L/kg (25 L in 70 kg adult), indicating distribution primarily in extracellular fluid. No extensive tissue binding.
Approximately 4.5 L/kg (range 2.3–9.6 L/kg), indicating extensive tissue distribution.
Oral bioavailability is 85% (range 75-95%). Food does not significantly affect absorption.
Oral: approximately 37–55% (first-pass metabolism); subcutaneous: approximately 100%.
GFR 30-59 m L/min: 5 mg once daily; GFR <30 m L/min: not recommended
GFR <50 m L/min: reduce dose by 50%; GFR <10 m L/min: avoid use.
Child-Pugh A: no adjustment; Child-Pugh B: 5 mg once daily; Child-Pugh C: not recommended
Child-Pugh Class B: reduce dose by 50%; Child-Pugh Class C: contraindicated.
Not established for patients <18 years
0.09 mg/kg/day IV over 2 hours for 7 consecutive days; or 0.14 mg/kg/day IV over 2 hours for 5 consecutive days (total dose 0.7 mg/kg per course). No specific pediatric dose adjustments beyond weight-based dosing.
No specific dose adjustment; monitor renal function
No specific dose adjustment recommended; monitor renal function and adjust accordingly.
There is no black box warning for Ekterly.
WARNING: Neurotoxicity and Hematologic Toxicity. Cladribine can cause severe bone marrow suppression (neutropenia, anemia, thrombocytopenia) and neurotoxicity (including paralysis, coma, and death). Dose-dependent and more frequent in high doses.
Hepatotoxicity: Monitor liver function tests prior to and during treatment; discontinue if significant transaminase elevation or jaundice occurs.,Gastrointestinal disorders: Severe nausea, vomiting, dyspepsia, and diarrhea; manage with antiemetics and supportive care.,Hypersensitivity reactions: including angioedema and anaphylaxis; discontinue if occur.,QT interval prolongation: Avoid use in patients with baseline QT prolongation or those on QT-prolonging drugs; monitor electrolytes.,Fetal harm: Can cause fetal harm; advise effective contraception in women of reproductive potential.
Myelosuppression: Monitor blood counts regularly; dose adjustment or discontinuation may be needed.,Neurotoxicity: Risk increased with high doses and in patients with renal impairment.,Nephrotoxicity: Use with caution in renal impairment; reduce dose if Cr Cl < 60 m L/min.,Hepatotoxicity: Monitor liver function tests.,Secondary malignancies: Increased risk of myelodysplasia and acute myeloid leukemia.,Infections: Increased susceptibility due to lymphopenia; consider prophylaxis.
Hypersensitivity to Ekterly or any excipients,Pregnancy,Lactation,Severe hepatic impairment (Child-Pugh C)
Hypersensitivity to cladribine or any component of the formulation.,Pre-existing severe bone marrow suppression (e.g., neutropenia, thrombocytopenia) unless due to underlying disease.,Pregnancy: Can cause fetal harm.,Lactation: Discontinue nursing or drug.
Avoid grapefruit and grapefruit juice due to CYP3A4 inhibition increasing upadacitinib exposure. No other significant food interactions known.
No significant food interactions. Avoid grapefruit juice due to potential CYP3A4 interaction (though minimal). Maintain adequate hydration to prevent tumor lysis syndrome in hematologic malignancies.
Insufficient human data; animal studies show fetal toxicity at maternal toxic doses. First trimester: potential risk of malformations; second/third trimester: risk of fetal growth restriction and oligohydramnios. Avoid use unless benefit outweighs risk.
FDA Pregnancy Category D. First trimester: Avoid due to known teratogenicity in animal studies (skeletal and visceral malformations) and potential for MDS and AML. Second and third trimesters: Risk of fetal myelosuppression, intrauterine growth restriction, and preterm labor. Cladribine crosses the placenta and may cause fetal hematopoietic suppression.
No human data; M/P ratio unknown. Drug likely excreted into breast milk due to low molecular weight. Use with caution, monitor infant for adverse effects.
Contraindicated during breastfeeding. Cladribine is excreted into human milk; M/P ratio not determined. Potential for severe adverse effects in nursing infants, including myelosuppression and immunosuppression. Discontinue breastfeeding during therapy and for at least 7 days after last dose.
No established dose adjustments in pregnancy. Increased plasma volume and renal clearance may reduce drug exposure; monitor clinical response and adjust empirically if needed.
No established dose adjustments in pregnancy. Use is contraindicated. If unavoidable, lowest effective dose and close monitoring for maternal and fetal toxicity. Pharmacokinetic changes in pregnancy (increased volume of distribution, renal clearance) may reduce exposure; however, risks outweigh benefits.
EKTERLY is a combination of upadacitinib and methotrexate for moderate-to-severe rheumatoid arthritis. Monitor for serious infections, thrombosis, and GI perforations. Check baseline and periodic lipids, LFTs, and CBC. Avoid use with strong CYP3A4 inhibitors or inducers.
Cladribine is a purine nucleoside analog that causes lymphocyte depletion, effective in hairy cell leukemia and multiple sclerosis. Monitor for severe lymphopenia, opportunistic infections (e.g., herpes zoster, tuberculosis), and delayed myelosuppression. Do not administer live vaccines during or after treatment. Due to high bioavailability after subcutaneous administration, adjust dose for renal impairment. Hypersensitivity reactions may occur; premedicate with antihistamines if needed.
Take EKTERLY exactly as prescribed. Do not stop without consulting your doctor.,Report any signs of infection, such as fever, cough, or skin redness, immediately.,Avoid live vaccines while taking EKTERLY. Update vaccinations before starting treatment.,Inform your doctor if you have a history of blood clots, stomach ulcers, or diverticulitis.,Use effective contraception during treatment and for at least 4 weeks after stopping.,Avoid grapefruit and grapefruit juice as they may increase side effects.
Cladribine can significantly lower your white blood cell count, increasing infection risk. Report fever, chills, or sore throat immediately.,Avoid live vaccines (e.g., MMR, shingles) during and for at least 6 months after treatment.,You may experience fatigue, nausea, headache, or skin reactions at injection site. These are common but report severe symptoms.,Use effective contraception during treatment and for at least 6 months after the last dose. Cladribine may harm a fetus.,You will need regular blood tests to monitor your blood cell counts, liver, and kidney function.
No interactions on record
"The combination of cabazitaxel and cladribine may potentiate myelosuppression due to overlapping bone marrow toxicity profiles. Cabazitaxel, a taxane antineoplastic, inhibits microtubule disassembly, while cladribine, a purine analog, incorporates into DNA and induces apoptosis in dividing and resting lymphocytes. Concurrent use increases the risk of severe neutropenia, thrombocytopenia, and anemia, potentially leading to febrile neutropenia or bleeding complications."
"Cladribine, a purine nucleoside analog with potent immunosuppressive properties, may reduce the pharmacodynamic effects of cardiac glycosides such as acetyldigitoxin. This interaction is hypothesized to occur through cladribine-induced modulation of myocardial cellular signaling pathways that decrease sensitivity to digitalis compounds, potentially leading to reduced inotropic efficacy. Clinically, this could manifest as diminished control of heart rate in patients with atrial fibrillation or worsening heart failure symptoms, particularly in those relying on acetyldigitoxin for rate control or inotropic support."
"The risk or severity of adverse effects can be increased when Pimecrolimus is combined with Cladribine."
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about EKTERLY vs CLADRIBINE, answered by our medical review team.
EKTERLY is a Antineoplastic Agent that works by Ekterly is a tissue-selective estrogen receptor degrader (SERD) that binds to the estrogen receptor (ER) and induces conformational changes leading to ER degradation. It antagonizes ER-mediated gene transcription and signaling, thereby inhibiting ER-dependent breast cancer cell proliferation.. CLADRIBINE is a Antineoplastic Agent that works by Cladribine is a purine nucleoside analog that is phosphorylated intracellularly to its active triphosphate form, which inhibits DNA synthesis and repair, leading to cell death, particularly in lymphocytes. It also depletes adenosine deaminase (ADA) and accumulates in cells with high deoxycytidine kinase activity.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between EKTERLY and CLADRIBINE depend on the specific clinical indication. These are both Antineoplastic Agent agents and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of EKTERLY is: 10 mg orally once daily. The standard adult dose of CLADRIBINE is: 0.09 mg/kg/day IV over 2 hours for 7 consecutive days; or 0.14 mg/kg/day IV over 2 hours for 5 consecutive days (total dose 0.7 mg/kg per course).. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between EKTERLY and CLADRIBINE in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. EKTERLY is classified as Category C. Insufficient human data; animal studies show fetal toxicity at maternal toxic doses. First trimester: potential risk of malformations; second/third trimester: risk of fetal growth . CLADRIBINE is classified as Category C. FDA Pregnancy Category D. First trimester: Avoid due to known teratogenicity in animal studies (skeletal and visceral malformations) and potential for MDS and AML. Second and third. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.