f) Protease inhibitors
Cinanserin , a known serotonin antagonist, which also showed
hopeful SARS-CoV inhibitory features, is another possible option to be
considered. It could inhibit the 3 chymotrypsin‐like protease and could
inhibit SARS‐CoV replication (45). The 3C-L protease is encoded in
SARS‐CoV2. Therefore, Cinanserin may be an effective therapy for the
COVID‐19 infection. Also, flavonoids like: Herbacetin, rhoifolin, and
pectolinarin are 3C‐like protease inhibitors (8).
Nelfinavir is an HIV-1 protease inhibitor previously used in HIV
treatment that acts through inhibition of 3C-L protein (45).
Carfilzomib is an approved anti-cancer drug which by inhibition
of proteasome shows potential for inhibiting COVID-19 protease (46).
Indinavir: It is an anti-HIV drug that based on molecular studies
can also be used against SARS-COV-2 by potentially inhibiting the viral
protease. Adverse effects are mostly of gastrointestinal and hepatic
symptoms (47, 48).
Danoprevir: It is another HCV NS3/4 protease inhibitor has also
shown potential according to the studies. It is also being used for
Hepatitis C treatment. Studies reveal a pharmacokinetic boost in
co-administration of danoprevir with ritonavir (49).
Ledipasvir and velpatasvir , NS5A protein inhibitors of HCV have
been proposed for further investigation due to virtual screening
studies. Ledipasvir and velpatasvir in combination withsofosbuvir have been used as a potent anti-hepatitis C treatment.
They may also cause headache, fatigue, and nausea as adverse effects
(50).
SARS-CoV-2 M protein is the main enzyme utilized by the virus for
replication, thus making it an appealing target. Studies suggest
multiple agents that may or may not be approved by the FDA. For example:Telaprevir and boceprevi r. These are α-ketoamide drugs
that target the main protease of coronaviruses and 3C protease of
enteroviruses and have a crucial role in the treatment of hepatitis C
(51).