Synthesis and evaluation of designed PKC modulators for enhanced cancer immunotherapy

Abstract

Bryostatin 1 is a marine natural product under investigation for HIV/AIDS eradication, the treatment of neurological disorders, and enhanced CAR T/NK cell immunotherapy. Despite its promising activity, bryostatin 1 is neither evolved nor optimized for the treatment of human disease. Here we report the design, synthesis, and biological evaluation of several close-in analogs of bryostatin 1. Using a function-oriented synthesis approach, we synthesize a series of bryostatin analogs designed to maintain affinity for bryostatin's target protein kinase C (PKC) while enabling exploration of their divergent biological functions. Our latestage diversification strategy provides efficient access to a library of bryostatin analogs, which per our design retain affinity for PKC but exhibit variable PKC translocation kinetics. We further demonstrate that select analogs potently increase cell surface expression of CD22, a promising CAR T cell target for the treatment of leukemias, highlighting the clinical potential of bryostatin analogs for enhancing targeted immunotherapies.

Humanized Mouse Models for the Advancement of Innate Lymphoid Cell-Based Cancer Immunotherapies

“…Drugs such as lenalidomide and pomalidomide can enhance antitumor ILC behavior as well ( 159 , 160 ). Bryostatins are protein kinase C modulators that are currently being engineered to improve CAR NK functionality ( 161 ). These and many other drugs have the potential to broadly or specifically activate NK cells or ILCs in addition to other immune cells within the TME.…”

Structural anatomy of C1 domain interactions with DAG and other agonists

“…Shortly after their discovery, PKCs were identified as cellular receptors for tumor-promoting phorbol esters 12 that bind C1 domains in lieu of DAG. These observations, combined with the central roles executed by PKCs in intracellular signaling established their DAG-sensing function as an attractive target for therapeutic intervention, with considerable promise in the treatment of Alzheimer's disease 13 , HIV/AIDS 14,15 , and cancer 16,17 . However, the structural basis of DAG recognition by the C1 domains remained elusive, and the strategies for therapeutic agent design deployed to date all relied on modeling studies (reviewed in 18 ) based on the single available crystal structure of the C1 domain complexed to a ligand that does not activate PKC 19 .…”

Designed PKC-targeting bryostatin analogs modulate innate immunity and neuroinflammation

“…Bryo-1 has anti-tumorigenic properties and has been tested in multiple human clinical trials of solid and hematologic malignancies (Clamp and Jayson, 2002). It is currently under investigation in pre-clinical or clinical studies of Alzheimer's disease (Farlow et al, 2019;clinicaltrials.gov, NCT03560245), HIV latency reversal (Bullen et al, 2014;Gutierrez et al, 2016;Laird et al, 2015;Sloane et al, 2020), and antigenic stimulation to augment CAR-T immunotherapy (Hardman et al, 2020;Ramakrishna et al, 2019).…”

“…We recently reported a scalable synthesis of bryo-1 that addresses the clinical supply problem and provides bryo-1 in quantities that enable the first-ever synthetic access to potentially efficacious close-in precursors and derivatives (Wender et al, 2017). Prior computational, synthesis, and assay work has established the functional importance of the distinct structural elements of bryo-1, identifying pharmacophoric elements critical for PKC binding and regulatory elements that impact ternary interactions with the plasma membrane ( Figure 1A) (Hardman et al, 2020;Ryckbosch, Wender, and Pande, 2017;Wender et al, 1986 and1988;Yang et al, 2018). Three hydrogen-bonding functionalities around the C-ring (C1 carbonyl, C19 hemiketal, and C26 hydroxyl) are critical for PKC binding, whereas the A and B rings determine interactions with the plasma membrane and regulate PKC translocation and downstream functions in biological systems.…”

“…These insights provided the basis for developing a platform of rationally designed bryologs that differ with regard to PKC binding and the kinetics of PKC activation, translocation, and down-regulation within cells, with divergent biological consequences. We recently used this approach to identify a set of bryologs that successfully upregulate cluster of differentiation-22 (CD22) surface expression on leukemia cells (Hardman et al, 2020), an important target for CAR-T immunotherapy (Ramakrishna et al, 2019).…”