Ongoing Research and Availability
There are currently no CCBs on the WHO list of drug candidates for SARS-CoV-2 infection:
https://www.who.int/blueprint/priority-diseases/key-action/Table_of_therapeutics_Appendix_17022020.pdf?ua=1.
To date, there is at least one clinical trial registered that employs CCBs in the context of COVID-19 (NCT04330300, Galway, Ireland). It is based around the observation that SARS-CoV-2 uses angiotensin converting enzyme 2 (ACE2) as a cell entry point, and that commonly prescribed antihypertensives, angiotensin converting enzyme inhibitors (ACE inhibitors) might have a detrimental effect on patients who contract COVID-19. The study thus compares patients who remain on ACE inhibitors throughout their illness with patients who are switched to alternative antihypertensives, including CCBs. While this work is not concerned with the mechanism of action discussed above, it will provide useful information on the potential therapeutic role of these drugs in SARS-CoV-2 infection.
No patents specifically relating to tetrandrine and the therapy of SARS-CoV-2 infection were found online (but see Chinese and US patents, cited above). However, a phase 4 clinical trial of tetrandrine for the treatment of SARS-CoV-2 was set up in China in March 2020, https://clinicaltrials.gov/ct2/show/NCT04308317, of one year’s duration. It is geared towards preventing pulmonary fibrosis, and does not mention a pharmacological basis for the mechanism of action of tetrandrine. However, primary and secondary outcome measures are stated as survival rate and body temperature, respectively, suggesting that the trial will provide valuable insights into the role of tetrandrine as an acute therapeutic agent.