Generic substitution: a need for clarification

Nonbioequivalent prescription drug interchangeability, concerns on patient safety and drug market dynamics in Brazil

Since the enforcement of Generics Act (1999), three types of pharmaceutically equivalent products are marketed in Brazil: innovative reference (REF), "similar" (S) and generic (G) drugs. The S (brand name) and G (generic name) borrow from REF (brand name) clinical data on safety and efficacy and dosage regimen. G (but not S) is bioequivalent to and interchangeable with REF. Starting in 2003, Brazilian Sanitary Surveillance Agency (Anvisa) has required data on relative bioavailability tests (with REF) to approve (or renew registration of) S drugs. In 2014, Anvisa extended interchangeability notion to similar drugs with a "comparable" bioavailability, i.e., an "equivalent" similar drug (EQ). Drugs for chronic diseases and "critical dose medicines" are listed among the EQ drugs approved. Interchangeability of nonbioequivalent medicines raises deep concerns regarding therapeutic failures and adverse events. Concerns are even more worrisome if patients switch from one drug to another during an ongoing treatment for illnesses such as epilepsy, congestive heart failure, hypertension, diabetes and/or substitutable drugs have a narrow therapeutic index.

Immunogenicity of Biotherapeutics: Causes and Association with Posttranslational Modifications

Today, potential immunogenicity can be better evaluated during the drug development process, and we have rational approaches to manage the clinical consequences of immunogenicity. The focus of the scientific community should be on developing sensitive diagnostics that can predict immunogenicity-mediated adverse events in the small fraction of subjects that develop clinically relevant anti-drug antibodies. Here, we discuss the causes of immunogenicity which could be product-related (inherent property of the product or might be picked up during the manufacturing process), patient-related (genetic profile or eating habits), or linked to the route of administration. We describe various posttranslational modifications (PTMs) and how they may influence immunogenicity. Over the last three decades, we have significantly improved our understanding about the types of PTMs of biotherapeutic proteins and their association with immunogenicity. It is also now clear that all PTMs do not lead to clinical immunogenicity. We also discuss the mechanisms of immunogenicity (which include T cell-dependent and T cell-independent responses) and immunological tolerance. We further elaborate on the management of immunogenicity in preclinical and clinical setting and the unique challenges raised by biosimilars, which may have different immunogenic potential from their parent biotherapeutics.

The Impact of Generic Substitution on Health and Economic Outcomes: A Systematic Review

BACKGROUND

Generic drugs are considered therapeutically equivalent to their original counterparts and lower in acquisition costs. However, the overall impact of generic substitution (GS) on global clinical and economic outcomes has not been conclusively evaluated.

OBJECTIVE

To test whether (1) generics and original products yield the same health outcomes, and (2) generic therapies save economic resources versus original therapies.

METHODS

We performed a systematic literature review in Medline, Embase, and the Cochrane Database of Systematic Reviews to identify original studies that examine clinical or economic outcomes of GS. After standardized data extraction, reported outcomes were categorized as supporting or rejecting the hypotheses. Each reported outcome was assessed and accounted for supporting and opposing GS. One publication could provide multiple outcome comparisons.

RESULTS

We included 40 studies across ten therapeutic areas. Fourteen studies examined patients on de novo therapy; 24 studies investigated maintenance drug therapy, and two studies considered both settings. Overall, 119 outcome comparisons were examined. Of 97 clinical outcome comparisons, 67% reported no significant difference between generic drugs and their off-patent counterparts. Of 22 economic comparisons, 64% suggested that GS increased costs. Consequently, hypothesis (1) was supported but hypothesis (2) was not. We found no major differences among studies that investigated clinical outcomes with de novo or maintenance therapy.

CONCLUSION

The review suggests that clinical effects are similar after GS. However, economic savings are not guaranteed. More systematic research comparing clinical and economic outcomes with or without GS is needed to inform policy on the use of generic substitution.

Deficiencies of the FDA in evaluating generic formulations: addressing narrow therapeutic index drugs

Generic drugs represent a significant portion of the medical arsenal in treating disease. As copies of originator drugs, these drugs have been permitted abbreviated approval under the Hatch-Waxman Act. Yet with the current cost focus upon generic formulations, potential safety issues with generics have arisen. Although there is an established criterion of "bioequivalence" that generic formulations must demonstrate, narrow-therapeutic index drugs for sensitive clinical circumstances such as epilepsy, antiplatelet therapies, and mental health treatments may require different regulatory treatment than other generic drugs. Further, in these circumstances, differences in generic formulations may lead to adverse clinical outcomes due to less stringent bioequivalence tolerances. Yet there is no mandate for comparison between different generic formulations. Countries outside the United States advocate for narrowing tolerance ranges for these high risk health situations and the drugs for their treatment. We argue in this paper that additional patient safety matters must be taken into account for narrow therapeutic disease drugs, and regulatory bodies should emphasize greater tightness in bioequivalence before these narrow-therapeutic drug generic formulations are approved.