TK2 (thymidine kinase 2) is a protein involved in the normal function of mitochondria. It helps to make and maintain the DNA in mitochondria.
TK2 deficiency, as the name suggests, occurs when a person has a genetic mutation that prevents them from making enough functional TK2. This leads to abnormally low amounts of DNA in mitochondria. Ultimately, the mitochondria are not able to provide the energy that cells need.
Most commonly, TK2 deficiency causes problems in muscles — presumably because muscle cells use a relatively high amount of cellular energy — and in more severe cases can affect the brain and liver, which also use a lot of energy. The most frequent symptoms are related to muscle weakness and difficulty moving.
MT1621 is, essentially, a group of deoxynucleosides — the ‘building blocks’ of mitochondrial DNA — that can be taken orally. The basic theory is that by providing more material to make the mitochondrial DNA, even a faulty system will make more.
In a retrospective Phase 2 clinical trial evaluating MT1621 (NCT03701568) in 38 people with TK2 deficiency, the treatment was reported to improve functional abilities relative to what would be expected in the disease’s natural course.
Patients who completed the earlier study, plus a few select others, were invited to continue (or start) using MT1621 in the open-label Phase 2 trial (NCT03845712) assessing its safety and effectiveness in up to 40 people with TK2 deficiency. This study is expected to conclude in December 2021.
To acquire Modis (and, by extension, MT1621), Zogenix reported paying $175 million in cash and $75 million in stock. Modis will also be eligible for an additional $150 million if MT1621 gets regulatory approvals, plus a 5% royalty on sales of MT1621 should it be approved.
“We welcome Modis to our growing Zogenix team,” Stephen J. Farr, PhD, the president and chief executive officer of Zogenix, said in a press release.
“With our strengthened portfolio, we are very excited to now be advancing two very promising potential new therapies to patients and families in need — FINTEPLA for Dravet and Lennox-Gastaut syndromes and MT1621 for TK2 deficiency,” he added.