Unique pharmacology of a novel allosteric agonist/sensitizer insulin receptor monoclonal antibody

Abstract

ObjectiveInsulin resistance is a key feature of Type 2 Diabetes (T2D), and improving insulin sensitivity is important for disease management. Allosteric modulation of the insulin receptor (IR) with monoclonal antibodies (mAbs) can enhance insulin sensitivity and restore glycemic control in animal models of T2D.MethodsA novel human mAb, IRAB-A, was identified by phage screening using competition binding and surface plasmon resonance assays with the IR extracellular domain. Cell based assays demonstrated agonist and sensitizer effects of IRAB-A on IR and Akt phosphorylation, as well as glucose uptake. Lean and diet-induced obese mice were used to characterize single-dose in vivo pharmacological effects of IRAB-A; multiple-dose IRAB-A effects were tested in obese mice.ResultsIn vitro studies indicate that IRAB-A exhibits sensitizer and agonist properties distinct from insulin on the IR and is translated to downstream signaling and function; IRAB-A bound specifically and allosterically to the IR and stabilized insulin binding. A single dose of IRAB-A given to lean mice rapidly reduced fed blood glucose for approximately 2 weeks, with concomitant reduced insulin levels suggesting improved insulin sensitivity. Phosphorylated IR (pIR) from skeletal muscle and liver were increased by IRAB-A; however, phosphorylated Akt (pAkt) levels were only elevated in skeletal muscle and not liver vs. control; immunochemistry analysis (IHC) confirmed the long-lived persistence of IRAB-A in skeletal muscle and liver. Studies in diet-induced obese (DIO) mice with IRAB-A reduced fed blood glucose and insulinemia yet impaired glucose tolerance and led to protracted insulinemia during a meal challenge.ConclusionCollectively, the data suggest IRAB-A acts allosterically on the insulin receptor acting non-competitively with insulin to both activate the receptor and enhance insulin signaling. While IRAB-A produced a decrease in blood glucose in lean mice, the data in DIO mice indicated an exacerbation of insulin resistance; these data were unexpected and suggested the interplay of complex unknown pharmacology. Taken together, this work suggests that IRAB-A may be an important tool to explore insulin receptor signaling and pharmacology.

The Insulin Receptor: An Important Target for the Development of Novel Medicines and Pesticides

“…The IR has recently made its mark as an attractive therapeutic target for a variety of cancers and diabetes in humans due to its overexpression in various cancers [ 13 , 32 ]. Thus, agonists and antagonists of the IR that selectively activate or inhibit the IIS pathway may have considerable value in providing promising drugs for human diseases [ 4 , 132 ]. However, in contrast to the diverse regulators of insulin, only a handful of modulators have been discovered for the IR [ 133 ].…”

Membrane Hormone Receptors and Their Signaling Pathways as Targets for Endocrine Disruptors

“…Insulin resistance is a key feature of Type 2 Diabetes (T2D), and improving insulin sensitivity is important for disease management. Therefore, an exciting challenge is the allosteric modulation of the insulin receptor (IR) with drugs [ 19 , 20 ]. As put forward before, drugs can lead to EDs emergence by dispersion of the drugs or their active metabolites in the environment.…”

Kinetics of Blood–Brain Barrier Transport of Monoclonal Antibodies Targeting the Insulin Receptor and the Transferrin Receptor

“…Estimates of the rate constants of an HIRMAb association, 1.0 × 10 5 M −1 sec −1 , which is equivalent to 0.006 nM −1 min −1 , and dissociation, 0.013 min −1 , with the soluble HIR ECD are available from the literature using SPR [81]. However, it is uncertain if such estimates are representative of HIRMAb binding to the IR that is embedded in the endothelial luminal membrane in vivo.…”

“…Only the parameters of simulation 15 produced a match between the experimentally observed brain uptake and the brain uptake predicted by the model (Figure 7). For the starting parameters, represented by simulation 11, the association rate constant (k 1 ) was set at 0.006 nM −1 min −1 [81], and the dissociation rate constant (k 2 ), 0.0056 min −1 , was computed from k 2 = k 1 •K D , where K D is the dissociation constant, 0.93 nM, of HIRMAb-IDUA fusion protein binding to the HIR ECD [35]. The endocytosis (k 3 ), exocytosis (k 7 ), and receptor recycling (k 6 ) rate constants in simulation 11 were taken from simulation 1 of the TfRMAb model (Figure 5).…”