Aptevo Soars on Reports of Complete Remission in AML


Positive data from an ongoing Phase Ib study has impressed investors in Aptevo Therapeutics. Following a clinical update that includes a complete remission in an acute myeloid leukemia patient, the company stock shot up more than 46% in premarket trading to $9.52 per share.

Seattle-based Aptevo reported the complete remission in an update on the company’s Ib expansion study assessing APVO436, a bispecific CD3xCD123 ADAPTIR, in the treatment of acute myeloid leukemia (AML).

In Cohort 1, a high-risk AML patient was treated with a combination of chemotherapy and APVO436 and achieved a complete remission (CR) after one cycle of therapy. The patient tolerated treatment without evidence of overt toxicity, the company announced this morning.

The primary endpoint of the Phase Ib study is to determine if treatment with APVO436 can improve the quality of remission in high-risk AML patients through the reduction of residual chemotherapy-resistant measurable residual disease (MRD) burden.

MRD in AML is when leukemia cells are present at very low numbers, but can be detected by highly sensitive flow cytometric or genomic methods. MRD negativity is associated with superior leukemia-free survival and overall survival. Aptevo said the quality of remission in study patients is assessed using “state-of-the art multiparameter flow cytometry methods for quantitative MRD assessment in a centralized laboratory.”

Based on the positive data seen in the Phase Ib study, Aptevo believes that APVO436 has the potential to help AML patients achieve complete remissions without MRD.

Additionally, the company said that treatment with APVO436 may be associated with a low risk of cytokine release syndrome and an increased likelihood of responses.

Marvin White, president and chief executive officer of Aptevo, said full data from the Phase Ib study is expected in the first half of 2022. The results from the study will determine its clinical strategy for the continued development of the experimental AML treatment.

Earlier this month at the Society for Immunology in Cancers (SITC) 2021 Annual Meeting, Hilario Ramos, senior director of immunobiology at Aptevo, touted preclinical data showcasing another oncology asset, APVO603. Ramos said APV0603 is a differentiated bispecific antibody with the potential to leverage the benefits of 4-1BB and OX40 in a single agent. During a presentation of preclinical data, Ramos said the experimental AML treatment can improve treatment options by targeting responses specifically to sites of active inflammation and limiting on-target toxicity.

“The data presented here demonstrate that this combination has the potential to promote anti-tumor responses two-fold. First, by improving the fitness of exhausted effector CD8+ T cells. Second, by reducing the potential for activation of suppressive responses by T regulatory subsets,” Ramos said at the SITC meeting. “This dual biological mechanism of action offers the potential for development of a compound that acts against both solid and hematologic tumors and in the presence of addition immunomodulatory treatments or modalities such as CAR T or adoptive immune cell therapies."

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