Medicare Part D Spending on Single-Enantiomer Drugs Versus Their Racemic Precursors

Chiral Resolution, Absolute Configuration Assignment, and Genotoxicity Evaluation of Racemic 3,4-Dihydroquinazoline as a Novel Anticancer Agent

If a new drug candidate will be a mixture of enantiomers, both enantiomers should be separately studied for at least latent genotoxicity as early as possible since the thalidomide tragedy. Our group has recently reported that KCP-10043F (OZ-001) as a racemate (±)-3,4-dihydroquinazoline derivative strongly represses the proliferation of human A549 lung cancer cells by caspase-mediated apoptosis via STAT3 inactivation. To investigate the possible teratological effects of the two enantiomers of a racemic KCP-10043F, therefore chiral resolution of (±)-KCP-10043F was performed and subsequently followed by a series of chemical processes to afford the corresponding chiral diastereomers. By using 1H NMR anisotropy method, the absolute configuration (+)-KCP-10043F and (−)-KCP-10043F could be assigned as S and R configuration, respectively. The bacterial reverse mutation test (Ames test) for racemate (±)-KCP-10043F and its two enantiomers exhibited that all three stereoisomers were found to be nongenotoxic against five bacterial strains with/without metabolic activation. In addition, (R)-(−)-KCP-10043F displayed almost equal anticancer activity to (S)-(+)-KCP-10043F against three cancer cell lines. Based on these overall results, racemate KCP-10043F (OZ-001) could be used for our ongoing preclinical and clinical studies without the expensive asymmetric process and/or chiral separation.

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

IMPORTANCE

Chiral switching, a strategy in which drug manufacturers develop a single-enantiomer formulation of a drug to be substituted for a racemic formulation, allows manufacturers to maintain market exclusivity for drugs losing patent protection, even without demonstrating superior efficacy or safety.

OBJECTIVE

To identify and characterize all randomized clinical trials (RCTs) directly comparing a Food and Drug Administration (FDA)-approved single-enantiomer drug against a previously approved racemic drug for 1 or more efficacy or safety end points.

EVIDENCE REVIEW

Drugs were identified using the Drugs@FDA database. Randomized clinical trials were identified using Ovid MEDLINE (1949 to October 22, 2019), Ovid Embase (1974 to October 22, 2019), Web of Science Core Collection (all years), ClinicalTrials.gov, and Cochrane Central Registry of Controlled Trials (CENTRAL, Wiley, Issue 8 of 12, October 22, 2019). Trials were characterized as favoring the single-enantiomer or racemic drugs based on whether the primary efficacy, secondary efficacy, and safety end points achieved each study's defined significance level (eg, P < .05). Trials were characterized as favoring neither drug if no statistically significant differences were reported for any end point or if both drugs were found to be superior for 1 or more separate end points.

FINDINGS

Fifteen FDA-approved single-enantiomer drugs were identified with racemic precursors approved in the US or Europe. For 3 single-enantiomer racemic drug pairs, no RCTs directly comparing the drugs were identified. For the remaining 12 pairs, 185 RCTs comparing efficacy or safety of the drug pairs were identified, 124 (67.0%) of which studied 1 pair (levobupivacaine/bupivacaine). There were 179 RCTs directly comparing drug pairs using efficacy end points, of which 23 (12.8%) favored the single enantiomer based on primary efficacy end point results. There were 124 RCTs directly comparing drug pairs using safety end points, of which 17 (13.7%) favored the single-enantiomer drug. For 9 of the 15 single-enantiomer drugs (60.0%), no RCTs were identified providing evidence of improved efficacy, based on primary end point results, or safety as compared with their racemic precursors.

CONCLUSIONS AND RELEVANCE

The results of this systematic review suggest that most newly marketed FDA-approved single-enantiomer drugs are infrequently directly compared with their racemic precursors, and when compared, they are uncommonly found to provide improved efficacy or safety, despite their greater costs.

FDA Approval and Regulation of Pharmaceuticals, 1983-2018

IMPORTANCE

US law requires testing of new drugs before approval to ensure that they provide a well-defined benefit that is commensurate with their risks. A major challenge for the US Food and Drug Administration (FDA) is to achieve an appropriate balance between rigorous testing and the need for timely approval of drugs that have benefits that outweigh their risks.

OBJECTIVE

To describe the evolution of laws and standards affecting drug testing, the use of new approval programs and standards, expansions of the role and authority of the FDA, and changes in the number of drugs approved from the 1980s to 2018.

EVIDENCE

Sources of evidence included principal federal laws and FDA regulations (1962-2018) and FDA databases of approved new drugs (1984-2018), generic drugs (1970-2018), biologics (1984-2018), and vaccines (1998-2018); special development and approval programs (Orphan drug [1984-2018], Fast-Track [1988-2018], Priority Review and its predecessors [1984-2018], Accelerated Approval [1992-2018], and Breakthrough Therapy [2012-2018]); expanded access (2010-2017) and Risk Evaluation and Mitigation Strategies (2008-2018); and user fees paid to the FDA by industry (1993-2018).

FINDINGS

From 1983 to 2018, legislation and regulatory initiatives have substantially changed drug approval at the FDA. The mean annual number of new drug approvals, including biologics, was 34 from 1990-1999, 25 from 2000-2009, and 41 from 2010-2018. New biologic product approvals increased from a median of 2.5 from 1990-1999, to 5 from 2000-2013, to 12 from 2014-2018. The median annual number of generic drugs approved was 136 from 1970 to the enactment of the Hatch-Waxman Act in 1984; 284 from 1985 to the enactment of the Generic Drug User Fee Act in 2012; and 588 from 2013-2018. Prescription drug user fee funding expanded from new drugs and biologics in 1992 to generic and biosimilar drugs in 2012. The amount of Prescription Drug User Fee Act fees collected from industry increased from an annual mean of $66 million in 1993-1997 to $820 million in 2013-2017, and in 2018, user fees accounted for approximately 80% of the salaries of review personnel responsible for the approval of new drugs. The proportion of drugs approved with an Orphan Drug Act designation increased from 18% (55/304) in 1984-1995, to 22% (82/379) in 1996-2007, to 41% (154/380) in 2008-2018. Use of Accelerated Approval, Fast-Track, and Priority Review for new drugs has increased over time, with 81% (48/59) of new drugs benefiting from at least 1 such expedited program in 2018. The proportion of new approvals supported by at least 2 pivotal trials decreased from 80.6% in 1995-1997 to 52.8% in 2015-2017, based on 124 and 106 approvals, respectively, while the median number of patients studied did not change significantly (774 vs 816). FDA drug review times declined from more than 3 years in 1983 to less than 1 year in 2017, but total time from the authorization of clinical testing to approval has remained at approximately 8 years over that period.

CONCLUSIONS AND RELEVANCE

Over the last 4 decades, the approval and regulation processes for pharmaceutical agents have evolved and increased in complexity as special programs have been added and as the use of surrogate measures has been encouraged. The FDA funding needed to implement and manage these programs has been addressed by expanding industry-paid user fees. The FDA has increasingly accepted less data and more surrogate measures, and has shortened its review times.