Evaluation of Trials Comparing Single-Enantiomer Drugs to Their Racemic Precursors: A Systematic Review

Area of Science:

• Pharmacology
• Drug Development
• Clinical Trials

Background:

• Chiral switching involves developing single-enantiomer drugs from existing racemic formulations.
• This strategy can extend market exclusivity for drugs nearing patent expiration.
• Often, this is done without demonstrating superior efficacy or safety compared to the original racemic drug.

Purpose of the Study:

• To systematically identify and analyze randomized clinical trials (RCTs) that directly compare single-enantiomer drugs approved by the Food and Drug Administration (FDA) against their racemic predecessors.
• To characterize the comparative efficacy and safety endpoints of these drug pairs based on available RCT data.

Main Methods:

• Searched multiple databases including Ovid MEDLINE, Embase, Web of Science, ClinicalTrials.gov, and CENTRAL for relevant RCTs.
• Identified FDA-approved single-enantiomer drugs with racemic precursors.
• Characterized trials based on primary, secondary efficacy, and safety endpoints, determining which drug, if any, demonstrated statistically significant superiority.

Main Results:

• Out of 15 identified single-enantiomer drugs, only 12 had direct comparative RCTs, with 185 trials in total.
• A significant majority of trials (67%) focused on levobupivacaine/bupivacaine.
• Only 12.8% of efficacy trials and 13.7% of safety trials favored the single-enantiomer drug.
• 60% of single-enantiomer drugs lacked RCT evidence of improved efficacy or safety over their racemic forms.

Conclusions:

• Direct comparisons between single-enantiomer drugs and their racemic precursors are infrequent.
• When direct comparisons are made, single-enantiomer drugs rarely demonstrate superior efficacy or safety.
• The findings suggest that chiral switching may not consistently yield clinically significant benefits despite potentially higher costs.