The vast majority of patients who started treatment with imatinib for gastrointestinal stromal tumors (GISTs) received a generic drug that did not have FDA approval for this indication, a large retrospective review showed.
Almost half of the 2,000 patients in the imatinib initiators review had chronic myeloid leukemia (CML), while about a third had GIST. Three years after the introduction of generic imatinib, more than 90% of patients in both groups received the generic, which had a label indication for CML but not for GISTs, reported Bryan S. Walsh, JD , from Brigham and Women‘s Hospital and Harvard Medical School in Boston
Overall, 85% of patients with CML, GIST, or another condition were initiated on a generic version of imatinib, the group wrote in the Journal of Clinical Oncology.
The findings highlight the FDA-approved practice of “skinny labeling,” which allows generic manufacturers to market their labels that include covered indications, such as the CML for generic imatinib, but exclude indications still under patent protection. Skinny labeling is at the center of legal disputes between patent-holding brand-name drug companies and generic makers, Walsh said. MedPage today.
The skinny label has its origins in the Hatch-Waxman Amendments which established an approval pathway for generic drugs, including the Abbreviated New Drug Application.
“The goal is to prevent the delay of generic drug approvals as a result of a drug gaining subsequent approvals for new diseases after the initial approved indication,” Walsh said. “If a manufacturer were to get another disease approved for their drug, they would get another patent [that would extend exclusive marketing rights]. Thin labels allow generic manufacturers to avoid [patented-protected indications] and come to market timely. »
Generic approvals with thin labeling have become increasingly common in recent years. In a previous study, Walsh and colleagues identified 56 brand name drugs with newly approved generics between 2015 and 2019 with lean labeling sensitivity, 24 of which were approved with lean labels. In the year prior to first generic approval, median net sales of branded drugs with full-size generics were $522 million, while median net sales of branded drugs with small-label generics were $522 million. $852 million.
In the present study, Walsh and colleagues examined the impact of lean labeling by means of indication-specific imatinib uptake. They identified patients covered by private insurance or Medicare Advantage plans who started imatinib from February 2016 (when the first generic became available) to September 2020. Generic versions of imatinib approved during this period had thin labels that included indications for CML but excluded GISTs.
Of the 2,000 patients included in the analysis, 934 (47%) started imatinib for an indication of CML, 686 (34%) for GIST and 380 (19%) for other or unknown indications. Generic use increased throughout the study period, surpassing 80% across all diagnostic groups in January 2017, one year after the first generic became available.
After adjusting for differences in patient characteristics, generic use at initiation was slightly but significantly higher in patients with CML than in those with the patented indication of GIST (88% versus 85%; HR 0.56, 95% CI 0.39-0.80, P
The median copayment for a 30-day supply of generic imatinib was $7 versus $40 for brand name imatinib (Gleevec). Co-payments for generic imatinib were highest for patients with low-income, unsubsidized Medicare Advantage plans ($162) and lowest for patients with commercial insurance ($0). Median copayments for brand name imatinib ranged from $1,730 for Medicare without low-income subsidy to $0 for high-deductible commercial insurance plans.
“These results really put the difference in median copays into perspective,” Walsh said. “If you compare a median copayment of $7 for a generic with a median copayment of $40 for the brand name drug, that’s a big gap for a one-month prescription. It’s kind of the key point here. [Skinny labeling] makes drugs more affordable for patients.”
A closely watched legal battle centered on skinny labeling could have a game-changing effect on the future of skinny labels. Last year, a federal appeals court ruled that generic maker Teva infringed GlaxoSmithKline’s patent protection for the cardiovascular drug carvedilol (Coreg) and reversed a $235 million court ruling. Legal wrangling continues in this case, but other potential plaintiffs and defendants have taken notice.
“We’re starting to see some sort of knock-off cases going through the lower courts,” Walsh said. “In one case, it’s not a generic manufacturer that’s being sued but a health insurer, based on their form. It’s going to be interesting to watch and see how the courts deal with a new type of defendant.”
To preserve the beneficial effects of lean labeling, federal regulators should take the lead in providing guidance, Walsh and coauthors said.
“[The carvedilol case] posed a threat to the lean labeling pathway, as it could discourage generic manufacturers from using this approach to introduce timely generic competition,” they wrote. “To optimize the use of the lean labeling pathway and protect generic manufacturers, the FDA and U.S. Patents Trademark Office should provide better guidance to manufacturers on how to legally market generics labeled lean, and the FDA should provide a public list of branded products that may qualify for lean labeling. »
The study was supported by the Commonwealth Fund and Arnold Ventures.
Rome reported honoraria from Blue Cross and Blue Shield of Massachusetts and research funding from the Anthem Public Policy Institute.
Walsh said he has no relevant relationship with the industry.