Enrico Patrucco

Abstract RAS oncogenes (collectively NRAS , HRAS and especially KRAS ) are among the most frequently mutated genes in cancer, with common driver mutations occurring at codons 12, 13 and 61 1 . Small molecule inhibitors of the KRAS(G12C) oncoprotein have demonstrated clinical efficacy in patients with multiple cancer types and have led to regulatory approvals for the treatment of non-small cell lung cancer 2,3 . Nevertheless, KRAS G12C mutations account for only around 15% of KRAS -mutated cancers 4,5 , and there are no approved KRAS inhibitors for the majority of patients with tumours containing other common KRAS mutations. Here we describe RMC-7977, a reversible, tri-complex RAS inhibitor with broad-spectrum activity for the active state of both mutant and wild-type KRAS, NRAS and HRAS variants (a RAS(ON) multi-selective inhibitor). Preclinically, RMC-7977 demonstrated potent activity against RAS-addicted tumours carrying various RAS genotypes, particularly against cancer models with KRAS codon 12 mutations ( KRAS G12X ). Treatment with RMC-7977 led to tumour regression and was well tolerated in diverse RAS-addicted preclinical cancer models. Additionally, RMC-7977 inhibited the growth of KRAS G12C cancer models that are resistant to KRAS(G12C) inhibitors owing to restoration of RAS pathway signalling. Thus, RAS(ON) multi-selective inhibitors can target multiple oncogenic and wild-type RAS isoforms and have the potential to treat a wide range of RAS-addicted cancers with high unmet clinical need. A related RAS(ON) multi-selective inhibitor, RMC-6236, is currently under clinical evaluation in patients with KRAS -mutant solid tumours (ClinicalTrials.gov identifier: NCT05379985).

Duchenne muscular dystrophy (DMD) is a progressive and fatal genetic disorder of muscle degeneration. Patients with DMD lack expression of the protein dystrophin as a result of mutations in the X-linked dystrophin gene. The loss of dystrophin leads to severe skeletal muscle pathologies as well as cardiomyopathy, which manifests as congestive heart failure and arrhythmias. Like humans, dystrophin-deficient mice (mdx mice) show cardiac dysfunction as evidenced by a decrease in diastolic function followed by systolic dysfunction later in life. We have investigated whether sildenafil citrate (Viagra), a phosphodiesterase 5 (PDE5) inhibitor, can be used to ameliorate the age-related cardiac dysfunction present in the mdx mice. By using echocardiography, we show that chronic sildenafil treatment reduces functional deficits in the cardiac performance of aged mdx mice, with no effect on normal cardiac function in WT controls. More importantly, when sildenafil treatment was started after cardiomyopathy had developed, the established symptoms were rapidly reversed within a few days. It is recognized that PDE5 inhibitors can have cardioprotective effects in other models of cardiac damage, but the present study reports a prevention and reversal of pathological cardiac dysfunction as measured by functional analysis in a mouse model of DMD. Overall, the data suggest that PDE5 inhibitors may be a useful treatment for the cardiomyopathy affecting patients with DMD at early and late stages of the disease.

Hemopexin (Hx) is a plasma glycoprotein mainly expressed in liver and, less abundantly, in the central and peripheral nervous systems. Hx has a high binding affinity with heme and is considered to be a major transport vehicle of heme into the liver, thus preventing both heme-catalyzed oxidative damage and heme-bound iron loss. To determine the physiologic relevance of heme-Hx complex formation, Hx-deficient mice were generated by homologous recombination in embryonic stem (ES) cells. The Hx-deficient mice were viable and fertile. Their plasma iron level and blood parameters were comparable to those of control mice and they showed no evidence of tissue lesions caused by oxidative damage or abnormal iron deposits. Moreover, they were sensitive to acute hemolysis, as are wild-type mice. Nevertheless, Hx-null mice recovered more slowly after hemolysis and were seen to have more severe renal damage than controls. After hemolytic stimulus, Hx-deficient mice presented prolonged hemoglobinuria with a higher kidney iron load and higher lipid peroxidation than control mice. Moreover, Hx-null mice showed altered posthemolysis haptoglobin (Hp) turnover in as much as Hp persisted in the circulation after hemolytic stimulus. These data indicate that, although Hx is not crucial either for iron metabolism or as a protection against oxidative stress under physiologic conditions, it does play an important protective role after hemolytic processes.

Hypertension affects nearly 20% of the population in Western countries and strongly increases the risk for cardiovascular diseases. In the pathogenesis of hypertension, the vasoactive peptide of the renin-angiotensin system, angiotensin II and its G protein-coupled receptors (GPCRs), play a crucial role by eliciting reactive oxygen species (ROS) and mediating vessel contractility. Here we show that mice lacking the GPCR-activated phosphoinositide 3-kinase (PI3K)gamma are protected from hypertension that is induced by administration of angiotensin II in vivo. PI3Kgamma was found to play a role in angiotensin II-evoked smooth muscle contraction in two crucial, distinct signaling pathways. In response to angiotensin II, PI3Kgamma was required for the activation of Rac and the subsequent triggering of ROS production. Conversely, PI3Kgamma was necessary to activate protein kinase B/Akt, which, in turn, enhanced L-type Ca(2+) channel-mediated extracellular Ca(2+) entry. These data indicate that PI3Kgamma is a key transducer of the intracellular signals that are evoked by angiotensin II and suggest that blocking PI3Kgamma function might be exploited to improve therapeutic intervention on hypertension.