DXP-593 and DXP-604 are two neutralizing antibodies against SARS-CoV-2, screened from the memory B cells specific for the viral spike protein harvested from more than 60 convalescent COVID-19 patients. The antibody discovery was accomplished by using the high-throughput single-cell transcriptome and VDJ sequencing technologies. In biological assays, DXP-593 demonstrated strong neutralizing activity against SARS-CoV-2 pseudoviruses and live viruses, with half maximal inhibitory concentration (IC50) measured as 1.2 ng/ml and 15 ng/ml, respectively. In rodent models infected with SARS-CoV-2, DXP-593 also showed a strong curative and preventive effect. The binding epitope of DXP604 is different from that of DXP593, and it also showed distinctly neutralizing activity. In addition, DXP-604 has a strong neutralizing ability against the Covid-Delta variant. The pairing of DXP593 and DXP604 are expected to be a highly competitive cocktail therapeutic option for the treatment of COVID-19 infections, especially in combatting drug resistance caused by viral mutations.
Phase I and II clinical trials of DXP-593 have recently been completed in the USA and other countries, while a phase I trial of DXP-604 has been completed in Australia. In China, the phase I clinical trials of DXP-593 and DXP-604 as mono-therapies have reached completion, while the phase II trial of the combinatorial therapy is under way.