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Phase II biotransformation reactions are essential for detoxifying and eliminating xenobiotics, including many pharmaceutical compounds. These reactions typically involve conjugation, the covalent attachment of polar endogenous groups such as glucuronic acid, sulfate, methyl, or acetyl moieties to functional groups introduced during Phase I metabolism. The resulting conjugates are more water-soluble, enabling efficient renal or biliary excretion.The major classes of Phase II enzymes include...
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Drug toxicities can be stratified into pharmacological, pathological, or genotoxic based on their mechanisms. The incidence and severity of these toxicities generally increase with the drug's concentration in the body and exposure time.Pharmacological toxicity is evident when the therapeutic effects of drugs overshoot into adverse reactions in a predictable, dose-dependent manner. Central nervous system (CNS) depression from barbiturates is a classic example, with effects escalating from...
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Using Delayed Toxicities to Re-evaluate Tolerability in Phase 2 Trials: A Case Example using Bortezomib.

Shing M Lee1, Yuan Zhang1, Lori M Minasian2

  • 1a Department of Biostatistics , Mailman School of Public Health, Columbia University , New York , NY , USA.

Cancer Investigation
|July 11, 2017
PubMed
Summary

Assessing long-term tolerability in cancer trials is challenging. Phase 2 trial data, following patients longer for efficacy, offers valuable insights into delayed toxicities of treatments like bortezomib.

Keywords:
Cumulative toxicitiesDelayed toxicitiesLong-term tolerabilityTolerable dose

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Area of Science:

  • Oncology
  • Clinical Trial Design
  • Pharmacovigilance

Background:

  • Dose-finding trials often lack sufficient patient follow-up for delayed toxicity assessment.
  • Advanced stage cancer patients frequently discontinue early, limiting long-term tolerability data.
  • Phase 2 trials offer extended patient monitoring, valuable for evaluating long-term treatment effects.

Purpose of the Study:

  • To evaluate the utility of phase 2 trial data for assessing long-term tolerability.
  • To analyze delayed toxicity rates of bortezomib in advanced stage cancer patients.
  • To inform future clinical trial design regarding patient follow-up and toxicity assessment.

Main Methods:

  • Analysis of data from two SWOG-conducted phase 2 bortezomib trials (N=172).
  • Comparison of treatment-related severe toxicity rates during cycle 1 versus extended administration.
  • Retrospective evaluation of patient follow-up data for tolerability assessment.

Main Results:

  • Initial severe toxicity rates in cycle 1 were 23% and 31%.
  • Severe toxicity rates increased significantly with extended bortezomib administration to 37% and 70%.
  • Extended patient follow-up in phase 2 trials revealed higher toxicity burdens.

Conclusions:

  • Phase 2 trial data provides crucial insights into long-term tolerability.
  • Extended administration of bortezomib is associated with substantially higher severe toxicity rates.
  • Future trial designs should incorporate longer patient follow-up to capture delayed toxicities.