Introducing a reactive carbonyl to a scaffold that does not otherwise have an electrophilic functionality to create a reversible covalent inhibitor is a potentially useful strategy for enhancing compound potency. However, aldehydes are metabolically unstable, which precludes the use of this strategy for compounds to be tested in animal models or in human clinical studies. To overcome this limitation, we designed ketone-based functionalities capable of forming reversible covalent adducts, while displaying high metabolic stability, and imparting improved water solubility to their pendant scaffold. We tested this strategy on the ferroptosis inducer and experimental therapeutic erastin, and observed substantial increases in compound potency. In particular, a new carbonyl erastin analog, termed IKE, displayed improved potency, solubility and metabolic stability, thus representing an ideal candidate future in vivo cancer therapeutic applications.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease selectively targeting motor neurons in the brain and spinal cord. The reasons for differential motor neuron susceptibility remain elusive. We developed a stem cell-based motor neuron assay to study cell-autonomous mechanisms causing motor neuron degeneration, with implications for ALS. A small-molecule screen identified cyclopiazonic acid (CPA) as a stressor to which stem cell-derived motor neurons were more sensitive than interneurons. CPA induced endoplasmic reticulum stress and the unfolded protein response. Furthermore, CPA resulted in an accelerated degeneration of motor neurons expressing human superoxide dismutase 1 (hSOD1) carrying the ALS-causing G93A mutation, compared to motor neurons expressing wild-type hSOD1. A secondary screen identified compounds that alleviated CPA-mediated motor neuron degeneration: three kinase inhibitors and tauroursodeoxycholic acid (TUDCA), a bile acid derivative. The neuroprotective effects of these compounds were validated in human stem cell-derived motor neurons carrying a mutated SOD1 allele (hSOD1 A4V). Moreover, we found that the administration of TUDCA in an hSOD1 G93A mouse model of ALS reduced muscle denervation. Jointly, these results provide insights into the mechanisms contributing to the preferential susceptibility of ALS motor neurons, and they demonstrate the utility of stem cell-derived motor neurons for the discovery of new neuroprotective compounds.