Assembly of nuclear dimers of PI3K regulatory subunits is regulated by the Cdc42-activated tyrosine kinase ACK.

Activated Cdc42-associated kinase (ACK) is an oncogenic nonreceptor tyrosine kinase associated with poor prognosis in several human cancers. ACK promotes proliferation, in part by contributing to the activation of Akt, the major effector of class 1A phosphoinositide 3-kinases (PI3Ks), which transduce signals via membrane phosphoinositol lipids. We now show that ACK also interacts with other key components of class 1A PI3K signaling, the PI3K regulatory subunits. We demonstrate ACK binds to all five PI3K regulatory subunit isoforms and directly phosphorylates p85α, p85ß, p50α, and p55α on Tyr607 (or analogous residues). We found that phosphorylation of p85ß promotes cell proliferation in HEK293T cells. We demonstrate that ACK interacts with p85α exclusively in nuclear-enriched cell fractions, where p85α phosphorylated at Tyr607 (pTyr607) also resides, and identify an interaction between pTyr607 and the N-terminal SH2 domain that supports dimerization of the regulatory subunits. We infer from this that ACK targets p110-independent p85 and further postulate that these regulatory subunit dimers undertake novel nuclear functions underpinning ACK activity. We conclude that these dimers represent a previously undescribed mode of regulation for the class1A PI3K regulatory subunits and potentially reveal additional avenues for therapeutic intervention.

Phase 3 efficacy and safety trial of proposed liraglutide biosimilar for reduction of glycosylated hemoglobin (HbA1c) in patients with Type 2 diabetes mellitus.

Liraglutide is indicated for glycaemic control in adults with Type 2 diabetes mellitus (T2DM) as an adjunct to diet and exercise. A proposed biosimilar of liraglutide (Levim Liraglutide) was investigated for efficacy & safety in a phase 3 study against the originator reference liraglutide (Victoza®) manufactured by Novo Nordisk A/S, Denmark. Patients aged 18-65 years of age with glycosylated hemoglobin (HbA1c) between 7 and 10 %, among other criteria, were included in the study. Patients were randomized 1:1 to receive daily doses of either Levim liraglutide or reference liraglutide for 24 weeks. The least square mean (standard error, SE) for the primary efficacy endpoint of reduction in HbA1c% at Week 24 was -1.09 (0.15)% for Levim liraglutide group and -1.04 (0.14)% for reference liraglutide. The upper bound of the confidence interval for treatment difference was less than the non-inferiority margin of 0.4 % at one-sided alpha of 0.025 (P-value = 0.0003). The secondary endpoints for proportion of patients achieving reduction in HbA1c, glycaemic level and weight, changes in cardiovascular parameters and the overall safety profiles of the study drugs were comparable. Levim liraglutide demonstrated non-inferior efficacy and similar safety to reference liraglutide and may be an option in treatment of T2DM (CTRI.nic.in, no. CTRI/2022/02/040261).