Lopinavir-ritonavir for SARS-CoV-2 infection: a systematic review

COVID-19 is a new disease caused by the virus called SARS-CoV-2 which first emerged in Wuhan, China, and has infected more than 651 million people across the globe in less than 18 months causing more than 6.6 million deaths. Considering the fast pace of contagion, it is fortunate that most of the patients (>80%) have been asymptomatic, or only exhibited mild symptoms. The virus is highly contagious, the incubation period ranges between 2 – 14 days and the infection is transmitted mostly by inhalation of droplets or touching contaminated surfaces and then touching eyes, mouth, and nose. The major clinical symptoms of the disease are fever, cough, fatigue, malaise, and breathlessness [1].

Lopinavir is an antiretroviral protease inhibitor widely used for the treatment of HIV. Ritonavir was the second protease inhibitor approved in 1996 for the treatment of HIV in the United States. Ritonavir was originally designed to inhibit HIV protease but its ability to inhibit cytochrome P450-3A4 is nowadays considered of greater value as it is more often used to increase the bioavailability of other antiretroviral drugs when it is co-administered [2].

This is not the first time that this drug was proposed as a treatment against coronaviruses. In 2003, during the emergence of SARS-CoV-1, after the screening of approved drugs, lopinavir was identified as having in vitro inhibitory activity against SARS-CoV-1. Lopinavir/ritonavir was also used in the case of MERS, where the treatment presented positive results against the virus [3].

As the structure of the SARS-CoV-2 virus was analyzed, a basis for identifying drugs that could prove useful in the battle against this new disease was created. As such, computer-aided drug design has the potential to play an important role in finding new active drugs. This is how it was revealed that LPV shows inhibitory reactions against the SARS-CoV-2’s main protease [4]. The main protease of the virus, also known as 3C-like protease, has an important role in viral replication and maturation. This 3C-like protease is common in the family of coronaviruses, showing a commonality of 96.1% when compared with the main protease of the SARS-CoV-1 virus. The drugs lopinavir and ritonavir have been shown to interact with the 3C-like protease residues [5].

A systematic literature search was conducted on PubMed and Google Scholar, from 2020 to 2022. The terms COVID-19, lopinavir, ritonavir, lopinavir-ritonavir, LPV/r, efficacy, and survival were used in different combinations on the two databases mentioned above. After the duplicate articles were removed from the generated list, the remainder of the publications were screened, by going through titles, abstracts, and finally, the full text, to identify the relevant papers. We included only observational or randomized clinical trials assessing the efficacy and safety of the combination drug lopinavir/ritonavir for hospitalized COVID-19 patients, written in English and published in peer-reviewed journals.

The initial search retrieved a number of 2694 studies from all the different combinations of the used terms. After filtering to only include clinical and observational trials, 267 studies remained. The next step was to take out the duplicates from the different searches that were conducted. This step yielded 95 studies. Further analysis was conducted on the title, abstract, and full text of the resulting articles, and in the end a number of 10 studies that best fit our criteria were included in the current review (Figure 1).

Figure 1.

In one randomized study, by Cao et al. (2020), out of 199 patients, with confirmed SARS-CoV-2 infection and a median age of 58, 99 were administered the LPV/r drug combination, while the remaining 100 were administered standard-of-care treatment. In the study population, 60.3% were male, with a percentage of 61.6% in the lopinavir-ritonavir group and 59% in the standard-of-care group. In this study, it was revealed that the rate of mortality on the 28^th day was lower in the group of patients that had received the antiretroviral treatment, but the difference between the two groups of patients did not present a statistical significance (19.2% vs 25%). Patients in the lopinavir–ritonavir group had a shorter stay in the intensive care unit (ICU) than those in the standard-of-care group (median, 6 days vs. 11 days), and the duration from randomization to hospital discharge was numerically shorter (median, 12 days vs. 14 days). In addition, the percentage of patients with clinical improvement at day 14 was higher in the lopinavir–ritonavir group than in the standard of care group (45.5% vs. 30.0%) [3].

Another retrospective observational study was conducted on 120 patients, of which 78 had received LPV/r treatment, while the rest only received standard of care. The lopinavir-ritonavir group presented a median age of 50 with a male population of 44.9%, while the standard of care group had a median age of 57 with 45.2% males. The study showed that the lot which had treatment with the drug combination initiated within 10 days from symptom onset, had a shorter duration of SARS-CoV-2 RNA shedding compared with the lot that did not receive lopinavir-ritonavir treatment (median 19 days vs. 28.5 days; p < 0.0001). However, this difference was not demonstrated in patients receiving the treatment after 10 days from the symptom onset (median 27.5 days vs. 28.5 days, p = 0.51). In this study, the authors also reported a significantly higher number of hospitalization days in the lopinavir-ritonavir group, compared with the standard of care group (median 23 days vs. 18.5 days, p<0.01) [6].

Lecronier et al. oversaw a retrospective observational study on 89 patients that were admitted to the ICU, from which 80 were included in the analysis. The patients were divided into three groups, the lopinavir-ritonavir group with an average age of 55 and a male population of 75%, the hydroxychloroquine group with an average age of 59 and 82% male population and the standard of care group with a mean age of 57 and a male population of 80%. The study focused on the need for treatment escalation and it can be seen that from a number of 22 patients (28%) who received only standard care, 9 (41%) needed treatment escalation. 20 (25%) patients received standard-of-care and lopinavir-ritonavir, 10 (50%) of them required the escalation of treatment, and 38 (47%) received standard-of-care and hydroxychloroquine, with 15 (39%) of them needing an escalation in their treatment. Patients from the three categories needed intubation, as such: 2 (9%) from the standard of care category, 1 (5%) from the lopinavir-ritonavir category, and 5 (13%) from the hydroxychloroquine category. There was no statistical difference between the need for treatment escalation for the three groups (p=0.567) [7].

In another retrospective, observational study, conducted on 65 patients, of which 34 received hydroxychloroquine, had a mean age of 64.3 ± 16.3 with a male population of 41.2%, and 31 who received LPV/r, with an average age of 64.3 ±14.6 with a population of 35.5% males, it was demonstrated that the lopinavir-ritonavir combination had a significantly shorter time to negative conversion of viral RNA, compared to patients treated with hydroxychloroquine, in mild to moderate COVID-19 (median 21 days vs. 28 days) [8].

Of the 72 patients, with mild to moderate disease, included in the retrospective observational study that was conducted by Lee et al. in 2021, 44 % were male and the average age was that of 35 years. The participants were split into two categories, 45 of them received the LPV/r drug combination, while 27 received hydroxychloroquine. It was observed that the progression of the disease was more common in the patients that were on hydroxychloroquine treatment than the ones that were receiving the lopinavir-ritonavir treatment (44% vs. 18%). The difference in the progression of the disease was deemed statistically significant, with a p - value of p = 0.030. [9]

Another study that compared the effects of lopinavir-ritonavir and hydroxychloroquine was conducted by Arabi et al. The randomized controlled trial included a number of 694 patients which were divided into four categories, the lopinavir-ritonavir category composed of 255 participants, the hydroxychloroquine category which included 50 participants, the combination category made up of 27 participants and the control category numbered 362 participants. The average age between the groups was similar, the LPV/r group registered a mean age of 61, the hydroxychloroquine group had an average age of 56.3, the combination group’s mean age was 60.3 and the control group registered an average age of 60.8. The study analyzed the composite ordinal scale of the number of respiratory and cardiovascular organ support-free days (OSFD) and the in-hospital mortality between the four groups. The median value of the OSFD in the case of the lopinavir-ritonavir group was 4, for the hydroxychloroquine group it was 0, and for the combination group, it was −1. For the control group, the value of OSFD was 6. The mortality rate of the patients in the three treatment groups was higher compared to the control group, the lopinavir-ritonavir group having registered 88 deaths out of 249 patients (35%), the hydroxychloroquine group had 17 deaths out of 49 patients (35%), the combination group registered 13 deaths out of 26 patients (50%), compared with the combination group that registered 106 deaths out of 353 patients (30%). The three treatment groups were registered to have decreased organ support-free days and reduced survival rates, compared to the control group [10].

A randomized study was conducted in March 2020, on 86 patients, of which 34 received lopinavir-ritonavir, 35 received arbidol and 17 were a control lot. The lopinavir-ritonavir group had a median age of 50.7 with 50% males, the arbidol group had a median age of 50.5 and a male population of 45.7%, and the control group had 44.3 as a median age with 41.2% male population. All patients were monitored for 21 days. The median value of the time of symptom onset to treatment was 3.5 days for the lopinavir-ritonavir group, 6 days for the arbidol group, and 5 days for the control lot. The difference between the three groups did not present a statistical significance, the p-value being p=0.371. As an outcome of the study, it was shown that the three groups did not present any statistical differences on day 7 and day 14 when it came to the rate of antipyresis, the rate of cough resolution, and the rate of improvement on chest CT imaging (p=0.206). It was also shown that 8 (23.52%) and 3 (8.57%) of those who had received lopinavir-ritonavir and arbidol, respectively progressed to severe or critical clinic status, however, the difference was not statistically significant [11].

As a common symptom of COVID-19 is fever, one retrospective observational study, conducted by Ye et al. took a closer look, on a lot of 47 patients, at the effects of the LPV/r drug combinations on this symptom. As such, it was demonstrated that the body temperature of patients who received the drug combination returned to normal in a shorter time, than those in the control group (median 4.8 ± 1.94 days vs. 7.3 ± 1.53 days), but there was no significant difference (p=0.0364). The study also documented the side effects and toxicity levels of the drug combination, and it was concluded that the LPV/r treatment did not show signs of toxicity, and the side effects that were encountered were deemed to be mild, mainly nausea, vomiting, and diarrhea [12].

Another observational study conducted by Kocayiğit et al. compared the effects of favipiravir and the lopinavir/ritonavir drug combination on a lot of critically ill patients. Of the 107 consecutive patients that were included in the study, 65 received favipiravir and 42 received the lopinavir-ritonavir drug combination. The demographical data of the two groups was similar, the median age for the favipiravir group was 69.8±12.6, while the LPV/r group had a median age of 70.6±12.7. The age difference between the two groups was not statistically significant. There was no statistical difference in the mortality of the two groups. From the patients that received favipiravir, a total number of 43 patients died (66.2%) and from the lopinavir-ritonavir group, a number of 23 patients were declared deceased (54.8%). The p-value was p=0.237. What presented statistical significance was the median ICU stay of the two groups. The favipiravir group had an average stay of 6.6 days, while the average stay in the ICU ward for the lopinavir-ritonavir group was 9 days. The p-value was p=0.01 [13].

One of the most comprehensive studies on the efficacy and safety of the lopinavir-ritonavir drug combination for the treatment of COVID-19 was conducted by Lowe et al. A total of 1215 patients were screened, of which a number of 240 satisfied the inclusion criteria. The study population was relatively young, with most of the patients being under the age of 55 (90%). It is also of note that 85% of the admitted patients did not present any comorbidities. The patients were randomized into four groups, a group that received favipiravir and placebo medication composed of 59 people, a group that received lopinavir-ritonavir and placebo medication with a number of 60 patients, another group that received a combination of favipiravir, lopinavir-ritonavir and placebo medication made up of 61 patients, and finally, a group that only received placebo medication, that was numbering 60 participants. One of the objectives of this randomized clinical trial was to compare the effects of the different kinds of medications administered on the SARS-CoV-2 viral load, considering the load registered on Day 1 with the load on Day 5 of therapy. What was observed and documented in the study was that no treatment had any significant effect on the viral load. The change in viral loads was compared with the placebo group for all three options of treatment. The favipiravir group registered a −0.57 log₁₀ copies/mL (95% confidence interval (CI) −1.21 to 0.07, p = 0.08) change in the viral load, compared with the placebo group. For the lopinavir-ritonavir group, the registered viral load change against the placebo group was that of −0.18 log₁₀ copies/mL (95% CI −0.82 to 0.46, p = 0.58). The study also looked at the drug interaction between favipiravir and lopinavir-ritonavir, but no significant results were registered. What is interesting in the combination group is that the viral change against the placebo group takes an antagonistic direction with a value of 0.59 log₁₀ copies/mL (95% CI −0.32 to 1.50, p = 0.20). Another topic of interest that the study covered was the adverse effects recorded between the four groups of participants. There was a total of 518 events reported in 80 % (191) of the patients. 57% (295) of the reported events had a direct relationship with the treatment. It was observed that the highest number of adverse effects were registered in the lopinavir-ritonavir group, where 93% of the participants assigned to that group reported adverse effects. The combination group also registered a great number of adverse effects among its participants, with 88% of the patients having adverse effects. The favipiravir and placebo groups had much lower numbers of observed adverse effects, with 46% of participants in the case of the favipiravir group and 35% in the case of the placebo group. The difference between the lopinavir-ritonavir and the placebo group presented a statistically significant difference, the p-value being p < 0.0001 [14].

The present paper is meant to be a systematic review of the lopinavir-ritonavir treatment in the context of COVID-19. Several studies assessing the efficacy of the LPV/r drug combination were selected, analyzed, and discussed. From the total number of studies, three compared the efficacy of the drug combination with the normal standard of care applied to the patients, four looked at the differences between the treatment with LPV/r versus treatment with hydroxychloroquine, one study analyzed the differences between lopinavir-ritonavir and arbidol, and finally, two of the included studies took a detailed look and compared the lopinavir-ritonavir drug combination with favipiravir.

One of the studies that compared lopinavir-ritonavir treatment with standard-of-care treatment found no benefit in adding LPV/r medication. It is worth mentioning that the participants of this study were critically ill patients that presented severe forms of COVID-19, and it is important to note that the participants who received the LPV/r treatment had a lower mortality rate at day 28 and a numerically lower period in the ICU, compared with the standard of care group. Another study that had a comparison with the standard-of-care treatment showed that patients who received the antiretroviral therapy in the first 10 days of symptom onset had a shorter duration of viral shedding. The study also records higher numbers in the case of hospitalization for the LPV/r group compared with the standard of care group.

Finally, the last study that compared LPV/r treatment with standard-of-care treatment, concluded that there was a more evident therapeutic effect in the group of participants that were receiving LPV/r treatment, when analyzing fever resolution, with a limited number of side effects.

One of the studies that compared the lopinavir-ritonavir drug combination with hydroxychloroquine looked at the treatment escalation that was needed for the different groups of participants and at the number of patients that needed intubation but failed to prove any statistical significance between the differences between the groups of participants. Another study comparing the effects of LPV/r with hydroxychloroquine, which was conducted on mild to moderate COVID-19 patients, associated the drug combination with a shorter time until viral clearance was achieved. Another study that compared the LPV/r treatment with hydroxychloroquine treatment is the one conducted by Lee et al., where it was observed that the patients on LPV/r had a slower progression of the disease compared to the hydroxychloroquine group. The last study from the lopinavir-ritonavir vs. hydroxychloroquine batch, painted both the antiviral treatments and their combination treatment in a negative light, as it was demonstrated that participants in the antiviral groups had a higher mortality rate and a lower number of organ support-free days.

The study that compared the LPV/r treatment against arbidol treatment and standard of care, concluded that there was no statistically significant difference between the three groups when compared at day 7 and day 14 of treatment. The disease progression was also compared between the groups, but no significance was found.

One of the two studies that compared the effects of favipiravir and lopinavir-ritonavir treatments in patients suffering from COVID-19, deemed that there was no significant difference between the mortality rates of the compared groups. What, in turn, showed a statistically significant difference was the median stay in the ICU ward, having concluded that the participants that received lopinavir-ritonavir had a longer stay in the intensive care unit compared to the favipiravir group. The last study included in the present paper, compared lopinavir-ritonavir, favipiravir, and their combination against a placebo group. The main outcomes that resulted from the study were that there was no significant difference when comparing the viral load on day 1 with the viral load on day 5, between the antiviral groups and the placebo group. Another outcome presented in the study was related to the adverse effects of the administered medications, and here it was demonstrated that the group which presented the most reported and observed adverse effects was the lopinavir-ritonavir one, closely followed by the combination group. The difference in the number of adverse effects between the lopinavir-ritonavir group and the placebo groups was deemed to have been statistically significant.

In the process of making our study, one limitation stood out the most, the absence of more quality double-blinded RCTs. Most of the studies used for comparison were observational, which, most of the time, provides a low quality of evidence. One thing, in particular, presented a high variance, the gap between the initial symptom onset and the initiation of treatment.

As seen in the presented studies, the efficacy of the LPV/r drug combination in the treatment of COVID-19 is still a subject that needs further debate. Some of the presented studies have shown clear improvements in the patients that received the drug combination, such as a lower mortality rate at day 28, a faster resolution of fever, but also a reduced shedding of the SARS-CoV-2 RNA, while other studies reported a high occurrence of adverse effects and no clear benefit compared with the standard of care treatment.