BPS 2023
A p27-targeting novel peptide inhibitor to address drug resistance of tumors
Natalia Zisman
Director of Chemistry, Manufacturing and Controls, Concarlo Therapeutics
ABSTRACT
The cell cycle is governed by the activity of the cyclin-dependent kinases (CDKs), and inappropriate activity of the G1 CDKs, CDK2 and CDK4/6, has been linked to cancer initiation and progression. Several marketed CDK4/6 inhibitors (CDK4/6i) have extended treatment options for metastatic breast cancer patients, yet currently no tolerable therapy exists once the patient’s tumor develops resistance to these targeted therapies. Several resistance mechanisms have been detected clinically, but all of these converge to increase CDK2 activity, which has led to the hypothesis that inhibiting CDK2 will be key to combating CDK4/6i-dependent resistance. CDK2 and CDK4/6 are specifically regulated by the CDK-interacting protein, p27Kip1. p27 functions as an “ON-OFF” switch causing the coordinated activity or inactivity of both CDK4/6 and CDK2. Breast tumor-related kinase (BRK, a 451-mer) phosphorylates p27 at Y88, activating CDK4/CDK2 and driving cell proliferation. An alternative splice variant of BRK, ALT-BRK (a 134-mer) has been shown to block p27 phosphorylation, inhibit CDK4/6 and CDK2 activity and reduce ER+ breast tumor growth in vivo, demonstrating the therapeutic potential of using an ALT-derivative as a peptide mimetic to bind to p27 to inhibit CDK2/4/6 activity.
Concarlo harnessed these insights to design Peptide Variants (CCLs) and generate smaller synthetic peptide therapeutic. We assessed sequences of ALT-BRK across 37 species to identify amino acids that are conserved and critical for ALT’s potency. Assays evaluated CCLs’ ability to inhibit BRK’s phosphorylation of p27 phosphorylation and to outcompete ALT-BRK’s binding to the p27-Cyclin D-CDK4 complex. Effective inhibitors underwent in vitro potency testing in normal and breast cancer cells. The lead variant underwent physico-chemical characterization across buffers, followed by manufacturing scale-up by different manufacturing routes.
To deliver peptide therapeutic to inhibit the intracellular p27 target, the final Drug Product was designed with components that enhance systemic circulation and intracellular delivery. Formulations underwent comprehensive evaluation for in vitro/in vivo performance, including efficacy, tolerability, and systemic exposure, showing evidence of good formulation tolerability and peptide presence at the tumor site.
BIO
Natalia is a Director of Chemistry, Manufacturing and Controls at Concarlo Therapeutics, a pre-clinical company developing novel therapies to drug p27, the direct inhibitor of CDK4/CDK6 and CDK2. Natalia has over 20 years of experience in lipid nanoparticle drug delivery field and has been involved in all aspects of liposome manufacturing, starting from early-stage formulation design, process development, scale-up and early clinical manufacturing. Prior to her current role, she held various positions at Evonik Vancouver laboratories, facilitating transition of customer projects through different stages of development, from proposal scoping to formulation development to early clinical manufacturing. Prior to Evonik, she worked at a number of Vancouver based drug delivery companies (CDRD/AdMare, Celator/Jazz, Inex), focusing on development of liposomal drug products. Natalia holds undergraduate degree in Chemistry from University of British Columbia.