Evaluating Safety, Pharmacokinetics and Clinical Benefit of Silmitasertib (CX-4945) in Subjects With Moderate COVID-19

Silmitasertib is a first-in-class small molecule drug that targets Casein Kinase 2 (CK2). Protein kinase CK2 phosphorylates key proteins required to trigger mechanisms vital for viral replication and also is involved in development of host anti-viral immune response. SARS-CoV-2 viral proteins interacting with many human host proteins affect multiple innate immune pathways. One of these key proteins dysregulated by SARS-CoV-2 is the protein kinase CK2. SARS-COV-2 upregulates CK2 to support viral replication, avoid innate immune response and spread virus to nearby cells. Overactivation of CK2 indirectly contribute to successful viral replication and development of cytokine storm.SARs-Cov-2-induced overexpression of CK2, while pharmacological inhibition of CK2 suppresses virus proliferation. CK2 signaling appears to be an important pathway hijacked by SARS-CoV-2.

Emerging pre-clinical and clinical data and results of independent efficacy evaluation conducted by Utah State University and UCSF COVID-19 research group and Senhwa Biosciences hypothesize that Silmitasertib (CX-4945) could potentially quell virus-provoked aberrant hyperactivation of the innate immune system by inhibition of upregulated CK2 protein kinase, preferentially restoring normal host cell cytokine regulation, and attenuating viral replication in patients with moderate to severe COVID-19, thereby preventing disease progression and improving clinical outcomes. Intended target patient population for treatment with Silmitasertib (CX-4945) are SARS-COV-2 positive patients with moderate to severe COVID-19, since in the moderate to severe stage of the disease infected cells actively produce viral proteins that dysregulate signaling pathways to allow viruses to manipulate host immune responses to create an environment more favorable for infection, that may not be observed in the initial or mild stage of the disease.

CX-4945 demonstrated remarkable clinical benefits under emergency IND authorization in a patient with COVID-19 pneumonia not responsive to remdesivir, dexamethasone and antibiotics and requiring supplemental oxygen. The patient recovered and was discharged from the hospital in five days of treatment with CX-4945.

The purpose of this open-label, randomized, 2 arm parallel-group controlled, interventional prospective exploratory study in 20 subjects is to evaluate safety, tolerability and pharmacokinetics of Silmitasertib (CX-4945) 1000 mg BID dose, to compare time to clinical recovery, and putative clinical benefit across treatment groups, and to evaluate anti-viral activities in COVID-19 patients.

Silmitasertib is a generally well-tolerated medication. Most adverse events reported were mild to moderate in severity. The most common toxicities associated with CX-4945 were gastrointestinal disorders, manageable with drug discontinuation or use of anti-diarrheal medication. Based on the currently available data, the identified or potential risks of the product do not outweigh its identified or potential benefits.