Developing a novel dual PI3K-mTOR inhibitor from the prodrug of a metabolite

Area of Science:

• Oncology
• Pharmacology
• Drug Development

Background:

• The phosphoinositide 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) pathway is a critical regulator of cell growth and survival, frequently dysregulated in cancer.
• Developing targeted inhibitors for this pathway presents challenges in achieving desired efficacy and pharmacokinetic profiles.

Purpose of the Study:

• To develop a novel PI3K-mTOR inhibitor by creating a prodrug of an active metabolite.
• To optimize drug delivery and therapeutic potential for cancer treatment.

Main Methods:

• Identification and characterization of a lead compound (compound 1) and its major active metabolite (compound 2).
• In vitro activity assays and in vivo tumor xenograft models to assess efficacy.
• Metabolism studies using liver microsomes from various species (mouse, rat, dog, human).
• Design and synthesis of a prodrug (compound 3) of the active metabolite to enhance solubility and bioavailability.

Main Results:

• Compound 1 demonstrated efficacy in a tumor xenograft model, but with low exposure.
• Compound 2, the major metabolite of compound 1, was identified as the active species responsible for in vivo efficacy.
• Metabolism of compound 1 to compound 2 occurred primarily in mouse liver microsomes, not in rat, dog, or human.
• Prodrug compound 3 showed rapid conversion to compound 2 but did not improve oral exposure.

Conclusions:

• The in vivo efficacy observed with compound 1 was attributed to its active metabolite, compound 2.
• Species-specific metabolism necessitates careful consideration for preclinical to clinical translation.
• While compound 3 (prodrug) improved solubility, further strategies are needed to enhance oral bioavailability, with intravenous administration being a potential future direction.