We found that after in three of four acute outpatient COVID-19 patients became afebrile within 48 hours; the empiric addition of baloxavir to nelfinavir may have been helpful. In contrast, the two subacute COVID-19 patients with predominant GI symptoms only responded partially to nelfinavir.
At time of writing (May 3, 2020), the NIH guideline states that “except in the context of a clinical trial, the COVID-19 Treatment Guidelines Panel (the Panel) recommends against the use of the following drugs for the treatment of COVID-19: Lopinavir/ritonavir (AI) or other HIV protease inhibitors (AIII) because of unfavorable pharmacodynamics and negative clinical trial data.”(11). Similarly, NEJM has commented that “for the Covid-19 pandemic and other pressing medical challenges, the health of individual patients and the public at large will be best served by remaining true to our time-tested approach to clinical trial evidence and drug evaluation, rather than cutting corners and resorting to appealing yet risky quick fixes.” (12) The NIH guideline on antiviral is based on the negative clinical study of lopinavir–ritonavir (13), which is much less potent than nelfinavir. But the fact remains for the frontline physicians that five months into the pandemic, we do not have an effective treatment for outpatient COVID-19 patients.
Based on in vitro antiviral activities and computational data, nelfinavir is among the strongest anti-SARS-CoV-2 candidate among medications easily accessible to North American physicians. While the anti-parasitic drug ivermectin, has also shown in vitro activity and has garnered media interest(14), the blood level required to kill the virus far exceed possible with dosage being used clinically.(15) In contrast, nelfinavir drug level in plasma, mononuclear cells, and lung achieved is significantly higher than the level required to kill the virus in vitro.(7)
In computer modeling by Japan National Institute of Infectious Disease, nelfinavir is predicted to decrease duration of illness by 4 days based on in vitro data (16) , similar to the decrease of hospitalization days seen with remdesivir. (6) In our cohort, three of four acute cases responded similarly to the response to the first US COVID-19 patient after remdesivir intravenous injection: fever and oxygenation saturation stabilized shortly after administration, while cough lasted longer. In contrast to the favorable response in our acute patients in our cohort, the two subacute patients with predominant GI symptoms had only partial effect to nelfinavir. GI involvement in COVID-19 is increasingly recognized. (17,18) The pathophysiology of COVID-19 GI tract involvement may be complex: in HIV enteropathy which has similar clinical presentation, GI tract continues to suffer from chronic inflammation and intestinal barrier dysfunction despite antiviral therapies (19,20). Prolonged antiviral therapies and additional therapies may be required to adequately address this problem.
Prior to our report, the media reported one successful case using nelfinavir in Shanghai in January 2020 (21). However, the drug has not been tested clinically in Europe and China because marketing authorization for nelfinavir has not been renewed in EU and in China by the pharmaceutical company(22,23). In US and Canada, despite being off patent, nelfinavir is only manufactured by one manufacturer with no generic options. The drug is not covered by many medical insurance plans and is approximately $700 per 2-week course. Nelfinavir can cause diarrhea in about 20% of HIV patients, and calcium carbonate was found to be helpful (24). Among our cohort, nelfinavir triggered or worsened diarrhea in two patients while it helped COVID-19 related diarrhea in two patients. Calcium carbonate, which has been recommended as a treatment of HIV nelfinavir-induced diarrhea, only had minimal effect for nelfinavir-induced diarrhea in our COVID-19 cohort. Aside from mild diarrhea and drug interaction, it is generally well tolerated; no dose adjustment is needed for renal failure and mild liver impairment. (25)
Baloxavir marboxil is an inhibitor of influenza virus cap-dependent endonuclease and has not been proven to be effective in COVID-19 (26). Many local practitioners have been using baloxavir for COVID-19 in our community, and we have decided to include the medication in the regimen for potential adjunctive effect.
If this encouraging experience is confirmed in clinical trial, nelfinavir will provide outpatient physicians an oral antiviral that can prevent patient hospitalization, especially for the patients with symptoms for less than two weeks. Like oseltamivir for influenza, nelfinavir may need to be given early to have maximal therapeutic effect.