Paxlovid (Nirmatrelvir/Ritonavir): A new approach to Covid-19 therapy?

Despite the need for novel, effective therapeutics for the COVID-19 pandemic, no curative regimen is yet available, therefore patients are forced to rely on supportive and nonspecific therapies. Some SARS-CoV-2 proteins, like the 3C-like protease (3CLpro) or the major protease (Mpro), have been identified as promising targets for antiviral drugs. The Mpro has major a role in protein processing as well as pathogenesis of the virus, and could be a useful therapeutic target. The antiviral drug nirmatrelvir can keep SARS-CoV-2 from replicating through inhibiting Mpro. Nirmatrelvir was combined with another HIV protease inhibitor, ritonavir, to create Paxlovid (Nirmatrelvir/Ritonavir). The metabolizing enzyme cytochrome P450 3 A is inhibited by ritonavir to lengthen the half-life of nirmatrelvir, so rintonavir acts as a pharmacological enhancer. Nirmatrelvir exhibits potent antiviral activity against current coronavirus variants, despite significant alterations in the SARS-CoV-2 viral genome. Nevertheless, there are still several unanswered questions. This review summarizes the current literature on nirmatrelvir and ritonavir efficacy in treating SARS-CoV-2 infection, and also their safety and possible side effects.

Outcomes of patients on dual-boosted PI regimens: experience of the Swiss HIV cohort study

Dual-boosted protease inhibitors (DBPI) are an option for salvage therapy for HIV-1 resistant patients. Patients receiving a DBPI in the Swiss HIV Cohort Study between January1996 and March 2007 were studied. Outcomes of interest were viral suppression at 24 weeks. 295 patients (72.5%) were on DBPI for over 6 months. The median duration was 2.2 years. Of 287 patients who had HIV-RNA >400 copies/ml at the start of the regimen, 184 (64.1%) were ever suppressed while on DBPI and 156 (54.4%) were suppressed within 24 weeks. The median time to suppression was 101 days (95% confidence interval 90-125 days). The median number of past regimens was 6 (IQR, 3-8). The main reasons for discontinuing the regimen were patient's wish (48.3%), treatment failure (22.5%), and toxicity (15.8%). Acquisition of HIV through intravenous drug use and the use of lopinavir in combination with saquinavir or atazanavir were associated with an increased likelihood of suppression within 6 months. Patients on DBPI are heavily treatment experienced. Viral suppression within 6 months was achieved in more than half of the patients. There may be a place for DBPI regimens in settings where more expensive alternates are not available.

Novel strategies in the use of lopinavir/ritonavir for the treatment of HIV infection in children

Lopinavir/ritonavir (LPV/r) is considered by many as the first choice protease inhibitor (PI) for children. This co-formulation avoids the need for children to take ritonavir separately to “boost” the levels of lopinavir. LPV/r has high virologic potency, an excellent toxicity profile and a high barrier to the development of viral resistance. However, LPV/r has poor tolerability of the oral suspension (due to the poor taste of ritonavir), difficult dosing requirements and metabolic side effects, especially hyperlipidemia. The new tablet low-dose formulation (100/25 mg) may allow more convenient antiretroviral treatment in children. Novel strategies of LPV/r in childhood could maximize its advantages. For example, infants infected with HIV despite single dose Nevirapine after birth need effective combination antiretroviral treatment. This can be given using a higher dose of LPV/r with therapeutic drug monitoring. Other novel uses include once daily LPV/r regimens in older children and adolescents and lower doses of LPV/r in certain populations, which may decrease hyperlipidemia. Heavily pre-treated children might benefit from a double PI/r regimen which includes LPV/r. The high potency of LPV/r needs to be balanced with convenient regimens, to enhance adherence and decrease toxicity whenever possible. The aim of this review is to discuss the rationale behind these novel strategies of LPV/r use in pediatric antiretroviral treatment as well as their results and limitations.