Pictilisib dimethanesulfonate (GDC-0941 2 MeSO3H salt) is a potent inhibitor of PI3Kα/δ with IC50 of 3 nM, with modest selectivity against p110β (11-fold) and p110γ (25-fold).

Pictilisib (GDC-0941) demonstrates high efficacy in inhibiting cell growth, inducing G0-G1 arrest, and promoting apoptosis, especially when used in combination with U0126. It shows increased sensitivity in H460 cells harboring PIK3CA mutations over A549 cells with wild-type PIK3CA, by diminishing PI3K pathway activity as evidenced by reduced pAK levels. Pictilisib significantly lowers VEGF secretion in the medium following hypoxic/anoxic conditions across all tested cell lines. In breast cancer cell model systems, Pictilisib, alongside RP-56976, considerably decreases tumor cell viability by 80% or more, surpassing the effects of single-agent treatments. It effectively inhibits Akt phosphorylation and affects downstream targets including pPRAS40 and pS6 in various tumor models such as Hs578T1.2 (PI3Kα wild-type), MCF7-neo/HER2 (PI3Kα-mutant), and MX-1 (PTEN-null). Furthermore, Pictilisib reduces the duration of RP-56976-induced mitotic arrest, leading to apoptosis, and exhibits strong antitumor activity against ZD1839-resistant NSCLC cell lines, A549 and H460, highlighting its potential as a therapeutic agent in cancer treatment.

Pictilisib (GDC-0941)-treated mice display substantial, non-linear tumor shrinkage that reverses upon cessation of treatment, indicating a dependency on continuous administration for sustained efficacy. At doses of 25 or 50 mg/kg, Pictilisib effectively diminishes tumor growth and inhibits the PI3K and HIF-1 pathways in eGFP-FTC133 tumor-bearing mice. Additionally, a higher dose of 150 mg/kg administered orally achieves tumor stasis in MCF7-neo/HER2 model animals. The combination of Pictilisib with RP-56976 facilitates tumor regression and enhances antitumor responses during the treatment regimen, suggesting a synergistic interaction between the two compounds.