Zoptarelin doxorubicin

Summary

Zoptarelin doxorubicin (AEZS‑108) is an investigational peptide‑drug conjugate that links the chemotherapy agent doxorubicin to a luteinizing hormone‑releasing hormone (LHRH) agonist. Designed to home in on tumor cells that express LHRH receptors, it is being evaluated for ovarian, endometrial, prostate and other solid cancers. Early‑phase clinical trials suggest modest antitumor activity with a toxicity profile that appears milder than free doxorubicin, but the compound remains experimental and is not approved for routine use.

Mechanism of Action

The LHRH agonist portion of zoptarelin doxorubicin binds with high affinity to LHRH receptors on the surface of certain tumor cells. Receptor binding triggers internalisation of the conjugate, delivering doxorubicin directly into the cancer cell where it intercalates DNA and inhibits topoisomerase II, leading to cell‑cycle arrest and apoptosis. In vitro the conjugate also inhibits the drug transporters OATP1B3 and OCT2, although physiologically based pharmacokinetic modelling predicts negligible impact on co‑administered drugs.

What the Research Shows

Phase II studies have examined zoptarelin doxorubicin in LHRH‑receptor‑positive ovarian (42 patients), endometrial (43 patients) and castration‑resistant prostate cancer (25 patients). In ovarian cancer, 14 % achieved partial responses and 38 % stable disease, with a median overall survival of about 53 weeks. Endometrial cancer showed 5 % complete and 18 % partial remissions, median time to progression of 7 months and overall survival of 15 months; neutropenia and leucopenia were the most common grade 3/4 toxicities. In prostate cancer, 52 % were progression‑free at 12 weeks, with one confirmed partial response and median progression‑free survival of 3.8 months. Pre‑clinical work demonstrated synergistic killing of triple‑negative breast cancer cells when combined with a glycolysis inhibitor, and physiologically based pharmacokinetic modelling indicated minimal drug‑drug interaction risk. A phase III trial in endometrial cancer failed to show superiority over free doxorubicin.

Reported Benefits

Across the studied indications, zoptarelin doxorubicin has shown measurable antitumor activity, including partial and complete responses, in patients whose disease had progressed after standard therapies. The targeted delivery concept appears to reduce the incidence of severe hematologic toxicity compared with conventional doxorubicin, and pharmacokinetic modelling suggests a low potential for clinically relevant drug‑drug interactions. These attributes support its investigation as a more selective chemotherapy option for LHRH‑receptor‑positive tumours.

Limitations of the Evidence

Evidence is limited to phase II trials with relatively small cohorts; no large phase III data demonstrate a clear survival advantage, and one phase III study in endometrial cancer did not outperform free doxorubicin. Response rates are modest and progression‑free intervals remain short. Efficacy appears confined to tumors that express LHRH receptors, necessitating reliable receptor testing. Long‑term safety, especially cardiac effects typical of anthracyclines, has not been fully characterised in the available abstracts.

Safety Considerations

The most frequently reported serious adverse events are hematologic, notably grade 3/4 neutropenia (≈12 %) and leucopenia (≈9 %) in endometrial cancer patients. Overall toxicity has been described as favorable compared with free doxorubicin, and physiologically based modelling predicts minimal inhibition of OATP1B3 and OCT2, reducing concern for drug‑drug interactions. Cardiac toxicity, a known risk of doxorubicin, was not specifically reported in the abstracts but remains a theoretical concern. Caution is advised in patients with pre‑existing bone‑marrow suppression.

How It Is Administered

Zoptarelin doxorubicin is administered intravenously as a 2‑hour infusion every 21 days. Dosing in trials has ranged from 210 mg/m² to 267 mg/m² (equimolar to approximately 76 mg/m² of free doxorubicin). Treatment cycles are typically continued until disease progression, unacceptable toxicity, or a maximum of 6–8 cycles, depending on the study protocol.

Routes of Administration

Goals & Uses

• Targeted cytotoxic deliveryEfficacyModerate
• Reduction of systemic doxorubicin toxicity via tumor targetingToxicity ReductionModerate
• Targeted treatment of ovarian cancerOncologyLow
• Targeted treatment of LHRH receptor-positive endometrial cancerOncologyModerate
• Treatment of LHRH‑positive solid tumorsIndicationModerate
• Targeted treatment of castration-resistant prostate cancerOncologyLow
• Reduced systemic cardiotoxicitySafetyModerate

Contraindications

• Severe pre-existing cardiomyopathy or heart failureCardiovascularHigh
• Known hypersensitivity to doxorubicinAllergyHigh
• Severe hepatic impairmentOrganModerateLiver function concerns
• Hypersensitivity to doxorubicin or LHRH analoguesAllergyHigh
• Pregnancy or lactationReproductiveHigh
• Severe cardiac dysfunction (ejection fraction < 50%)CardiacHigh
• Cumulative anthracycline dose at or near maximum lifetime limitOncologyHigh

Adverse Effects

• CardiotoxicityCardiovascularUncommon
• AlopeciaDermatologicCommonHair loss
• Hot flashesEndocrine / VasomotorUncommon
• Nausea/vomitingGastrointestinalCommon
• Hot flashes / hormonal effectsEndocrineUncommon
• Fatigue and astheniaConstitutionalCommon
• Nausea and vomitingGastrointestinalCommon
• MyelosuppressionHematologicCommon
• Myelosuppression (neutropenia, anemia, thrombocytopenia)HematologicalCommon

Drug Interactions

• Anticoagulants (e.g., warfarin)Moderate
• Live vaccinesHigh
• CYP3A4 inhibitors (e.g., ketoconazole)Moderate
• Other anthracyclinesHigh
• Other anthracyclines or cardiotoxic agentsHigh
• CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin)Moderate

Population Constraints

• PregnancyReproductive SafetyAbsolute
• Pediatric patientsAgeRelative
• Patients with LHRH receptor-negative tumorsBiomarkerRelative
• BreastfeedingReproductiveAbsolute
• Elderly (>75 years)GeriatricRelative

Regulatory Status

• European UnionInvestigationalNo EMA marketing authorization.
• United StatesInvestigationalPhase II/III trials discontinued; not FDA approved.
• United KingdomInvestigationalNot MHRA approved.

Completed Phase II trials; Phase III discontinued; not approved in major jurisdictions.

Evidence & Sources

• A physiologically based pharmacokinetic (PBPK) parent-metabolite model of the chemotherapeutic zoptarelin doxorubicin-integration of in vitro results, Phase I and Phase II data and model application for drug-drug interaction potential analysis
  Journal ArticleModerateHanke N, et al.2018-01-01T00:00:00.000000Z
• Efficacy and safety of AEZS-108 (INN: zoptarelin doxorubicin acetate) an LHRH agonist linked to doxorubicin in women with platinum refractory or resistant ovarian cancer expressing LHRH receptors: a multicenter phase II trial of the ago-study group (AGO GYN 5)
  Journal ArticleModerateEmons G, et al.2014-01-01T00:00:00.000000Z
• A Phase II Trial of AEZS-108 in Castration- and Taxane-Resistant Prostate Cancer
  Journal ArticleModerateYu SS, et al.2017-01-01T00:00:00.000000Z
• Efficacy and safety of AEZS-108 (LHRH agonist linked to doxorubicin) in women with advanced or recurrent endometrial cancer expressing LHRH receptors: a multicenter phase 2 trial (AGO-GYN5)
  Journal ArticleModerateEmons G, et al.2014-01-01T00:00:00.000000Z
• The Role of Gonadotropin-Releasing Hormone (GnRH) in Endometrial Cancer
  Journal ArticleHighEmons G, Gründker C2021-01-01T00:00:00.000000Z
• Inhibition of aerobic glycolysis enhances the anti-tumor efficacy of Zoptarelin Doxorubicin in triple-negative breast cancer cells
  Journal ArticleLowGründker C, et al.2019-01-01T00:00:00.000000Z

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