Discovery of an inhibitor of insulin-like growth factor 1 receptor activation: implications for cellular potency and selectivity over insulin receptor

Insulin-like growth factor 1 receptor (IGF-1R) is an attractive target for anti-cancer therapy due to its anti-apoptotic effect on tumor cells, but inhibition of insulin receptor (IR) may have undesired metabolic consequences. The primary sequences of the ATP substrate-binding sites of these receptors are identical and the crystal structures of the activated kinase domains are correspondingly similar. Thus, most small-molecule inhibitors described to date are equally potent against the activated kinase domains of IGF-1R and IR. In contrast, the non-phosphorylated kinase domains of these receptors have several structural features that may accommodate differences in binding affinity for kinase inhibitors. We used a cell-based assay measuring IGF-1R autophosphorylation as an inhibitor screen, and identified a potent purine derivative that is selective compared to IR. Surprisingly, the compound is a weak inhibitor of the activated IGF-1R tyrosine kinase domain. Biochemical and structural studies are presented that indicate the compound preferentially binds to the ATP site of non-phosphorylated IGF-1R compared to phosphorylated IGF-1R. The potential selectivity and potency advantages of this binding mode are discussed.

[Nontraumatic rhabdomyolysis: its etiology and the predictive factors of acute kidney failure]

BACKGROUND

The aim of this study was to determine the causes of non traumatic or medical rhabdomyolysis (RM) and analyze the clinical and biologic characteristics, as well as the predictive factors of acute renal failure (ARF).

METHODS

Fifty-nine patients with RM admitted to the Internal Medicine Department over an 18-month period were prospectively studied. The patients were classified into etiologic groups. Anamnesis, physical exploration and general analytical studies including creatinkinase, myoglobin, aldolase, magnesium and proteinogram were performed. Urine sodium was determined in patients with ARF>

RESULTS

Myalgias in 14 patients (23.7%) and a decrease in strength in 11 patients (18.6%) were the main clinical manifestations observed. As a sole cause, convulsion was the most frequent manifestation in 11 patients (18.6%) followed by muscular compression in 10 patients (16.9%). In the plurietiologic group the most frequent manifestation was muscular compression in 5 patients (16.9%) followed by alcoholism in 4 patients (6.7%). No differences were found in either the clinical manifestation or the biology of the RM among the different etiologies. Eight patients presented ARF (13.5%) with one patient requiring dialysis, and good response being observed with conservative treatment in 5 patients. On multivariant analysis the statistically significant ARF predictive factors were: age over 70 years (p = 0.003), nonketotic hyperosmolar diabetic coma (p = 0.01), previous dehydration (p = 0.001) and initial uric acid levels greater than or equal to 6 mg/dl (p = 0.002).

CONCLUSIONS

The clinical expression of rhabdomyolysis was small with the most frequent manifestations being convulsions and muscular compression. The predictive factors for acute renal failure were advanced age, nonketotic hyperosmolar diabetic coma, dehydration, and hyperuricemia.