ObesityWeek® research on Nov. 3 demonstrates gaps in drug labeling for people with obesity

SAN ANTONIO, Tx - Cancer patients need a lot of drugs—immunotherapies, chemotherapies, and anti-infectives. But new research at ObesityWeek® on Nov. 3, 2024, shows clinicians may not have all the information they need to use these drugs safely if the patient has obesity. For example, about half of U.S. oncologists are unaware of prolonged risks for interactions with a common antifungal drug and cancer drugs in persons with obesity. 

Currently, the FDA does not require medications seeking approval to be tested in people with obesity (PwO), and drug manufacturers often exclude PwO from clinical trials, despite the fact that 40% of Americans have obesity. This means PwO are prescribed drugs every day that may not be labeled appropriately for their use.  

Posaconazole, a widely used antifungal, is an example of such a drug. It inhibits a key liver enzyme that is important for breaking down many prescription drugs, including drugs for treating cancer. Because of this, oncologists and hematologists typically halt these kinds of oncology drugs while their patients are using posaconazole and for a period afterward. At least 20 oncology drug labels have instructions to delay giving the full dose during and after coadministration with posaconazole—delays that are almost always delineated in half-lives. Clinicians know they need to wait for a certain number of half-lives before restarting these oncology drugs because their label states how many half-lives to wait.  

However, posaconazole’s label doesn’t disclose the half-life for PwO. It only discloses the half- life for people with a normal BMI, whereas the half-life for PwO is nearly twice as long. Because this information has not been disclosed in the posaconazole label, clinicians may return PwO to full oncology drug doses too soon.  

The research shows the real-world impact of this oversight. In a survey of 100 oncologists and hematologists who prescribe posaconazole and oncology drugs that must follow half-life-based delay instructions, the majority were unaware of posaconazole’s extended half-life in PwO. Furthermore, the survey showed 85% of doctors look to the posaconazole label for this information, with 87% expecting the obesity half-life information to be included.  

Once clinicians were aware of the prolonged half-life, 100% said this information is essential for good clinical practice. This illustrates the importance of updating posaconazole’s drug label.  

“The data gathered from clinicians who currently prescribe posaconazole in people with obesity show us that there is a real gap in physician awareness and unfair disparities among patient populations,” stated Dr. Caroline Apovian, who is presenting the research and is a past president of the Obesity Society and Professor of Medicine at the Harvard Medical School. “Critical information needed by physicians for the safe use of posaconazole in people with obesity is not available in posaconazole’s drug label and it needs to be. People with obesity and their doctors deserve to know.”  

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