Tasidotin

Summary

Tasidotin (ILX651) is an investigational synthetic peptide derived from dolastatin‑15, developed as an antimitotic anticancer agent. It is administered intravenously and has been evaluated in early‑phase clinical trials for various advanced solid tumours. The compound targets microtubules to halt cell division, showing modest tumour responses and disease stabilisation in a limited number of patients.

Mechanism of Action

Tasidotin is a dolastatin‑15 analogue that binds to tubulin, disrupting microtubule polymerisation and dynamics. By preventing the formation of functional mitotic spindles, it induces mitotic arrest and subsequent apoptotic cell death in rapidly dividing cancer cells. This tubulin‑binding activity underlies its antimitotic and cytotoxic effects.

What the Research Shows

Three Phase I studies have examined tasidotin on different dosing schedules (weekly, daily for five days, or on days 1, 3, 5 every three weeks) in patients with advanced solid tumours. The recommended Phase II doses ranged from 27.3 to 46.8 mg/m² depending on schedule. The principal dose‑limiting toxicity was neutropenia; non‑hematologic adverse events were generally mild. Antitumour activity was observed as a complete response in a melanoma patient, a minor response in non‑small‑cell lung cancer, and disease stabilisation in several others. Pre‑clinical xenograft models demonstrated dose‑dependent tumour growth delay in lymphoma, myeloma, breast, and prostate cancers, with a comparatively higher IC₉₀ for human bone‑marrow colony formation than for mouse marrow.

Reported Benefits

Early clinical data suggest tasidotin can produce objective responses (e.g., complete remission in melanoma) and durable disease stabilisation in a subset of patients, while exhibiting a toxicity profile that may be milder than some other antitubulin agents (e.g., limited neuropathy and no cardiovascular effects). Pre‑clinical studies support broad antitumour activity across multiple tumour types.

Limitations of the Evidence

Evidence is confined to Phase I trials with small cohorts; no Phase II or randomized data exist to confirm efficacy or optimal dosing. Neutropenia is dose‑limiting, and the therapeutic window remains narrow. Comparative effectiveness versus established chemotherapies has not been established, and the drug has not achieved regulatory approval for any indication.

Safety Considerations

The most common and dose‑limiting adverse effect is neutropenia, occasionally leading to fever or infection. Other reported toxicities include mild‑to‑moderate diarrhea, vomiting, transaminase elevations, fatigue, alopecia, nausea, and mild neurosensory symptoms. Cardiovascular toxicity and severe cumulative neuropathy, observed with some dolastatin analogues, were not reported. Pharmacokinetics show a short plasma half‑life (<45–55 min) with limited accumulation after repeated dosing.

How It Is Administered

Tasidotin is delivered intravenously, typically as a 30‑minute infusion. Clinical studies have used three schedules: weekly infusion for three weeks of a 28‑day cycle, daily infusion for five consecutive days every three weeks, or infusions on days 1, 3, and 5 every three weeks. Formulations are provided as a hydrochloride salt for IV use.

Routes of Administration

Goals & Uses

• Solid tumor treatmentOncologyModerate
• Antimitotic cancer therapyOncologyModerate
• Hematologic malignancy treatmentOncologyLow

Contraindications

• Severe hepatic impairmentOrganHighLiver function concerns
• PregnancyPopulationHighPotential fetal risk or insufficient safety data
• Severe pre-existing neuropathyNeurologicalModerate

Adverse Effects

• Peripheral neuropathyNeurologicalUncommon
• AlopeciaDermatologicUncommonHair loss
• ConstipationGastrointestinalUncommonReduced bowel frequency or difficulty passing stool
• Nausea and vomitingGastrointestinalCommon
• NeutropeniaHematologicCommonLow neutrophil count
• FatigueGeneralCommonLow energy or tiredness

Drug Interactions

• CYP3A4 inhibitors (e.g., ketoconazole)Moderate
• Other myelosuppressive agentsHigh

Population Constraints

• Pediatric patientsAgeRelative
• Elderly patients (>75 years)AgeRelative
• Pregnant or lactating womenReproductiveAbsolute

Regulatory Status

• European UnionInvestigationalNo EMA approval; limited European clinical trial participation.
• United StatesInvestigationalStudied under IND; never received FDA approval. Development discontinued after Phase II.

Tasidotin has not received regulatory approval in any jurisdiction. It was studied under IND status in the United States as an investigational anticancer agent. Development appears to have stalled after Phase II trials showed insufficient efficacy.

Evidence & Sources

• Phase I and pharmacokinetic study of tasidotin hydrochloride (ILX651), a third-generation dolastatin-15 analogue, administered weekly for 3 weeks every 28 days in patients with advanced solid tumors
  Journal ArticleModerateMita AC, et al.2006-01-01T00:00:00.000000Z
• A phase I study of the dolastatin-15 analogue tasidotin (ILX651) administered intravenously daily for 5 consecutive days every 3 weeks in patients with advanced solid tumors
  Journal ArticleModerateEbbinghaus S, et al.2005-01-01T00:00:00.000000Z
• Bone marrow CFU-GM and human tumor xenograft efficacy of three tubulin binding agents
  Journal ArticleLowKurtzberg LS, et al.2009-01-01T00:00:00.000000Z
• Tasidotin HCl (Genzyme)
  Journal ArticleModerateRasila KK, Verschraegen C2005-01-01T00:00:00.000000Z
• Phase I and pharmacokinetic study of the dolastatin-15 analogue tasidotin (ILX651) administered intravenously on days 1, 3, and 5 every 3 weeks in patients with advanced solid tumors
  Journal ArticleModerateCunningham C, et al.2005-01-01T00:00:00.000000Z
• Gateways to clinical trials
  Journal ArticleModerateBayes M, Rabasseda X, Prous JR2006-01-01T00:00:00.000000Z

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