Potent GCN2 Inhibitor Capable of Reversing MDSC-Driven T Cell Suppression Demonstrates In Vivo Efficacy as a Single Agent and in Combination with Anti-Angiogenesis Therapy.

General control nonderepressible 2 (GCN2) protein kinase is a cellular stress sensor within the tumor microenvironment (TME), whose signaling cascade has been proposed to contribute to immune escape in tumors. Herein, we report the discovery of cell-potent GCN2 inhibitors with excellent selectivity against its closely related Integrated Stress Response (ISR) family members heme-regulated inhibitor kinase (HRI), protein kinase R (PKR), and (PKR)-like endoplasmic reticulum kinase (PERK), as well as good kinome-wide selectivity and favorable PK. In mice, compound 39 engages GCN2 at levels ≥80% with an oral dose of 15 mg/kg BID. We also demonstrate the ability of compound 39 to alleviate MDSC-related T cell suppression and restore T cell proliferation, similar to the effect seen in MDSCs from GCN2 knockout mice. In the LL2 syngeneic mouse model, compound 39 demonstrates significant tumor growth inhibition (TGI) as a single agent. Furthermore, TGI mediated by anti-VEGFR was enhanced by treatment with compound 39 demonstrating the complementarity of these two mechanisms.

Novel Piperidinyl-Azetidines as Potent and Selective CCR4 Antagonists Elicit Antitumor Response as a Single Agent and in Combination with Checkpoint Inhibitors.

The C-C chemokine receptor 4 (CCR4) is broadly expressed on regulatory T cells (Treg) as well as other circulating and tissue-resident T cells. Treg can be recruited to the tumor microenvironment (TME) through the C-C chemokines CCL17 and CCL22. Treg accumulation in the TME has been shown to dampen the antitumor immune response and is thought to be an important driver in tumor immune evasion. Preclinical and clinical data suggest that reducing the Treg population in the TME can potentiate the antitumor immune response of checkpoint inhibitors. We have developed small-molecule antagonists of CCR4, featuring a novel piperidinyl-azetidine motif, that inhibit the recruitment of Treg into the TME and elicit antitumor responses as a single agent or in combination with an immune checkpoint blockade. The discovery of these potent, selective, and orally bioavailable CCR4 antagonists, and their activity in in vitro and in vivo models, is described herein.

Discovery of a Potent and Selective CCR4 Antagonist That Inhibits Treg Trafficking into the Tumor Microenvironment.

Recruitment of suppressive CD4+ FOXP3+ regulatory T cells (Treg) to the tumor microenvironment (TME) has the potential to weaken the antitumor response in patients receiving treatment with immuno-oncology (IO) agents. Human Treg express CCR4 and can be recruited to the TME through the CC chemokine ligands CCL17 and CCL22. In some cancers, Treg accumulation correlates with poor patient prognosis. Preclinical data suggests that preventing the recruitment of Treg and increasing the population of activated effector T cells (Teff) in the TME can potentiate antitumor immune responses. We developed a novel series of potent, orally bioavailable small molecule antagonists of CCR4. From this series, several compounds exhibited high potency in distinct functional assays in addition to good in vitro and in vivo ADME properties. The design, synthesis, and SAR of this series and confirmation of its in vivo activity are reported.

DABO Boronates: Stable Heterocyclic Boronic Acid Complexes for Use in Suzuki-Miyaura Cross-Coupling Reactions.

Diethanolamine complexed heterocyclic boronic acids (DABO boronates) are air-stable reagents that can be used directly in Suzuki-Miyaura reactions in the presence of water or a protic co-solvent. Interestingly, heterocyclic DABO boronates can be stored for extended periods of time at room temperature with no noticeable degradation, unlike their boronic acid counterparts. Heterocyclic DABO boronates constitute an operationally simple and efficient alternative to other boronic acid derivatives as coupling partners in palladium catalyzed cross-coupling reactions under standard Suzuki-Miyaura conditions.

Allyl transfer to aldehydes and ketones by Brønsted acid activation of allyl and crotyl 1,3,2-dioxazaborolidines.

Alkyl dioxazaborolidines are air-stable and often crystalline organoboranes. A variety of Brønsted acids activate allyl dioxazaborolidines to generate reactive allyl-transfer reagents in situ. These reagents add to aldehydes and ketones to generate the corresponding alcohols in good yields under mild conditions. The E- and Z-crotyl reagents react diastereoselectively with aldehydes and ketones to produce anti and syn adducts, respectively, a result consistent with a cyclic transition state (type I mechanism).