Quetzal revives Syros's shelved asset

Quetzal Therapeutics has finally posted its registrational trial of QTX-2101 on clinicaltrials.gov. The Quatro-APL study, which was announced as initiated in December, will evaluate the asset, an oral formulation of arsenic trioxide, against an intravenous formulation in acute promyelocytic leukaemia, with pharmacokinetics and molecular CR rates as primary endpoints. The asset has had a somewhat tortuous path to this point. Syros Pharmaceuticals acquired it in December 2020 as part of its $12m takeout of Orsenix, only to halt its development in 2023. At the end of 2024, Syros's lead project, tamibarotene, failed in phase 3, triggering a default on a loan with Oxford Finance. To help settle the Oxford loan Syros sold the asset to Quetzal Therapeutics in February 2025; while the amount was not disclosed, Syros paid Oxford a total of $6m to settle the account, so this could be close to the value. Not much data on QTX-2101 (formerly SY-2101) have been made public, but according to Quetzal the phase 3 trial is based on positive pharmacokinetic results from a study sponsored by Syros that compared QTX-2101 versus an intravenous formulation of arsenic trioxide, something that might refer to a 12-patient test published in 2020.