Umbralisib (Ukoniq, TG Therapeutics) is an orally available PI3K delta inhibitor, targeting the delta isoform with nanomolar potency and several fold selectivity over the alpha, beta, and gamma isoforms of PI3K. The delta isoform of PI3K is strongly expressed in cells of hematopoietic origin and is believed to be important in the proliferation and survival of B-cell lymphocytes. On February 5, 2021, the Food and Drug Administration granted accelerated approval to umbralisib for the following indications: adult patients with relapsed or refractory marginal zone lymphoma (MZL) who have received at least one prior anti-CD20-based regimen; adult patients with relapsed or refractory follicular lymphoma (FL) who have received at least three prior lines of systemic therapy. However, on June 1, 2022, the FDA withdrew its approval for the cancer medicine Ukoniq due to safety concerns.