Hanmi Pharmaceutical has made Canadian biotech Aptose Biosciences a wholly owned subsidiary. The leadership of development for tuspetinib, a candidate treatment for acute myeloid leukemia (AML) that had been licensed out, will also return to Hanmi Pharmaceutical.
According to Aptose on the 6th, the company completed the acquisition process on the 30th of last month (local time) through Hanmi Pharmaceutical and its U.S. subsidiary, HS North America. As a result, Aptose was delisted from the Toronto Stock Exchange (TSX) on the 3rd and was incorporated as a wholly owned subsidiary of Hanmi Pharmaceutical.
The acquisition, first announced in Nov. last year, was finalized after a contract revision in Feb. this year. Hanmi Pharmaceutical will acquire in cash all Aptose's outstanding common shares, excluding the equity it already holds, at C$2.41 per share. This is a price 28% higher than the volume-weighted average price (VWAP) on the Toronto Stock Exchange over the 30 trading days immediately before the contract was signed.
The transaction received approval from Aptose shareholders and a Canadian court in Mar., followed by approval from Korean regulators, and was finalized. It was initially scheduled to be completed in Jan. this year, but the timeline was postponed several times as the domestic regulatory review dragged on.
The collaboration between Hanmi Pharmaceutical and Aptose began with a technology license-out. In 2021, Hanmi Pharmaceutical signed a technology export contract worth a total of $420 million, including rights to develop and commercialize tuspetinib. Subsequently, as global biotech investment contracted and Aptose's finances deteriorated, clinical development also faced setbacks.
Hanmi Pharmaceutical continued equity investment and funding support to keep the clinical program going. After Aptose fell into complete capital impairment last year and was delisted from Nasdaq this year, Hanmi chose to acquire all remaining shares. The industry estimates that Hanmi Pharmaceutical has invested more than $41 million in developing tuspetinib.
The triplet regimen of tuspetinib plus azacitidine and venetoclax recorded a composite complete remission rate (CRc) of 78.1% for newly diagnosed AML patients in an interim analysis of phase 1/2 trials. Composite complete remission is an indicator that combines complete remission (CR), in which blood counts fully recover, and remission with partial recovery.
All seven patients with FLT3 mutations achieved remission, posting a composite complete remission rate of 100%, while the rate among FLT3 wild-type patients was 72.0%. Seven of 10 patients with TP53 mutations/complex karyotype, considered the worst prognosis subtype, also achieved remission.
This is evaluated as meaningful in that, unlike existing therapies that target specific genetic mutations, it confirmed treatment effects across diverse mutant patient groups. Aptose has presented a strategy to develop tuspetinib as a first-line AML therapy usable regardless of mutation type.
With the acquisition completed, Hanmi Pharmaceutical will decide the future development strategy. A Hanmi Pharmaceutical official said, "We are conducting a reassessment of the candidate" and noted, "We plan to flesh out the development strategy later." Regarding the development lead, the official added, "We are keeping all options open, including direct development."