Sublingual Administration of All-Trans Retinoic Acid in Two Patients With Acute Promyelocytic Leukemia and Previous Gastric Bypass: A Case Series.

Standard treatments for acute promyelocytic leukemia (APL) are well established and highly effective, including all-trans retinoic acid (ATRA), which is an orally administered drug that targets the hallmark APL-associated PML:RARA fusion protein. However, patients who have undergone gastric bypass may have reduced oral drug bioavailability due to altered gastrointestinal anatomy, and sublingual rather than oral administration of ATRA may be required to optimize systemic absorption. Here, we describe two patients with APL who had previously undergone gastric bypass surgery and had a suboptimal initial response to oral ATRA therapy. Both patients showed substantial improvement in regard to their complete blood count parameters after switching to sublingual ATRA, suggesting that this route of administration may be needed for individuals with APL who have altered gastrointestinal anatomy that may lead to suboptimal bioavailability. Overall, the pharmacodynamics of ATRA in patients with conditions affecting systemic drug absorption require further investigation.