D18 is an immune modulator that acts as a dual agonist for TLR7/8 (with EC50 values of 24 nM for hTLR7 and 10 nM for hTLR8, respectively). It enhances the expression of PD-L1 through epigenetic regulation, thereby increasing the sensitivity of tumors to PD-1/PD-L1 blockade. Additionally, D18 functions as a cytotoxin for ADC synthesis, specifically for the ADC HE-S2 [1].
11-cis Retinal is a chromophore that binds to opsin in the mammalian visual system as an inverse agonist forming the inactive conformation of rhodopsin. When 11-cis retinal absorbs a photon of light, it isomerizes to form all-trans retinal beginning the phototransduction cycle, which is the basis for mammalian vision. A G121L mutation in opsin allows 11-cis retinal to bind as a partial agonist and activate rhodopsin in the absence of light. In a moth model of carotenoid deficiency-induced low visual sensitivity, 11-cis retinal application to compound eyes restored visual sensitivity almost completely.