Benzinga | Jun 11, 2021 02:17PM EDT

Aptose Biosciences Stock Tumbles As Luxeptinib Fails To Impress At EHA2021 Virtual Congress

* Aptose Biosciences Inc (NASDAQ:APTO) highlighted data from its luxeptinib currently in two Phase 1 a/b trials - one in relapsed or refractory acute myeloid leukemia (AML) and another in relapsed or refractory B cell malignancies.

* In Relapsed or Refractory AML or High-Risk MDS trial, APTO-253 has been well-tolerated in the patients treated at 20, 40, 66, 100, and 150 mg/m2 over multiple cycles supporting continued dose escalation.

* APTO-253 monomer rapidly transformed to and co-existed with the Fe(253)3 conjugate in peripheral blood.

* Serum levels of APTO-253 and the Fe(253)3 conjugate were dose-proportional, with significantly higher Fe(253)3 conjugate concentrations than monomer.

* In Relapsed or Refractory B-Cell Malignancies, the anti-tumor activity observed in multiple patients, including follicular lymphoma (FL), Waldenstrom's (WM), Chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL).

* Tumor reduction in a patient with follicular lymphoma (FL) upon dose escalation from 450 mg to 600 mg.

* IgM reduction in a patient with Waldenstrom's (WM) at 750mg dose.

* Dose escalation well-tolerated from 150 -- 600 mg twice daily over multiple cycles.

* One apparent dose-limiting toxicity of hypertension led to expansion at 750 mg -- upon further review appears unlikely related.

* Currently treating patients with B-cell malignancies at 750 mg BID in cohort 5; continued dose escalation planned.

* See the slide presentation here.

* Price Action: APTO shares are down 31.5% at $3.79 during the market session on the last check Friday.