Exploring the 1,3-benzoxazine chemotype for cannabinoid receptor 2 as a promising anti-cancer therapeutic

The discovery of selective agonists of cannabinoid receptor 2 (CB₂) is strongly pursued to successfully tuning endocannabinoid signaling for therapeutic purposes. However, the design of selective CB₂ agonists is still challenging because of the high homology with the cannabinoid receptor 1 (CB₁) and for the yet unclear molecular basis of the agonist/antagonist switch. Here, the 1,3-benzoxazine scaffold is presented as a versatile chemotype for the design of CB₂ agonists from which 25 derivatives were synthesized. Among these, compound 7b5 (CB₂ EC₅₀ = 110 nM, CB₁ EC₅₀ > 10 μM) demonstrated to impair proliferation of triple negative breast cancer BT549 cells and to attenuate the release of pro-inflammatory cytokines in a CB₂-dependent manner. Furthermore, 7b5 abrogated the activation of extracellular signal-regulated kinase (ERK) 1/2, a key pro-inflammatory and oncogenic enzyme. Finally, molecular dynamics studies suggested a new rationale for the in vitro measured selectivity and for the observed agonist behavior.