Shares of Aptevo Therapeutics Inc. (NASDAQ:APVO) dropped 18% on Tuesday even after the company disclosed positive interim clinical data for mipletamig, its investigational therapy for acute myeloid leukemia (AML).
Aptevo said mipletamig, when administered alongside venetoclax and azacitidine, produced an 86% clinical benefit rate in newly diagnosed AML patients who are elderly or otherwise not candidates for intensive chemotherapy. The company also reported that there were no instances of cytokine release syndrome among all frontline patients treated.
Among the 28 frontline patients considered evaluable from the RAINIER trial combined with a completed dose expansion cohort, Aptevo reported that 79% achieved either complete remission (CR) or complete remission with incomplete blood marker recovery (CRi), while 61% achieved complete remission. The company further stated that 55% of patients who achieved remission experienced blast reductions that reached measurable residual disease-negative (MRD-negative) thresholds.
Aptevo noted that four patients treated to date went on to receive allogeneic stem cell transplants. The company highlighted that 35% of those who achieved remissions carried the TP53 genetic mutation, a biomarker commonly associated with high-risk disease and poorer prognosis in AML.
"The emerging mipletamig data in frontline AML are highly encouraging and highlight the differentiated profile we believe is needed to advance treatment in frontline AML," said Dirk Huebner, Chief Medical Officer of Aptevo Therapeutics.
The RAINIER study is described by the company as a Phase 1b/2 dose-optimization, multi-center trial enrolling adults aged 18 years or older with newly diagnosed AML who are ineligible for intensive induction chemotherapy. Aptevo specified that the Phase 1b portion of the trial uses 28-day treatment cycles across sequential cohorts.
Despite the positive clinical readouts, the stock decline indicates that investors may be weighing uncertainties about Aptevo's path to bring mipletamig to market and the capital that may be required to support further development and commercialization efforts.
Key points
- Aptevo reported an 86% clinical benefit rate for mipletamig combined with venetoclax and azacitidine in newly diagnosed, elderly or unfit AML patients.
- Clinical outcomes among 28 evaluable frontline patients included 79% CR/CRi and 61% CR, with 55% of remitters achieving MRD-negative blast reductions.
- The market reaction may reflect investor concern about commercialization strategy and funding needs, impacting biotech and healthcare sector sentiment.
Risks and uncertainties
- Investor concern regarding the company’s path to commercialization could pressure the stock and affect biotech sector valuations.
- Potential capital requirements to advance development and commercialization may create financing risk for Aptevo and influence investor appetite for similar clinical-stage biotech companies.
- The report does not address next regulatory steps or timelines, leaving uncertainty about the development pathway.