Covid-19: High-dose chloroquine disphosphate shows potential efficacy but safety concerns

GlobalData Healthcare 20th April 2020 (Last Updated April 20th, 2020 17:16)

Covid-19: High-dose chloroquine disphosphate shows potential efficacy but safety concerns

On Tuesday 7 April, preliminary results for a Phase II study being conducted by Fundação de Medicina Tropical D Heitor Vieira Dourado for high-dose chloroquine disphosphate for Covid-19 patients were published. The study showed hazardous side effect of a QTc prolongation, resulting in the high-dose arm being halted. Despite this, results for low-dose chloroquine disphosphate (CQ) are still pending and enrolment is still continuing. A full set of Phase II results is required to identify any potential efficacy in the low-dose CQ arm for Covid-19 patients.

The 440-patient randomised, double-blinded Phase II study had patients taking high CQ for ten days. However, only 81 patients have been recruited for both arms so far, and the limited population size does not provide adequate results for high-dose CQ to be considered a safe drug for Covid-19 patients. Due to CQ not being recommended for Covid-19 at a national level, data from this study was compared to historical data from literature to establish potential safety hazards.

The high-dose arm identified prolonged QTc (25%) and a trend towards lethality (17%) compared to the lower dosage. Out of 14 patients with paired samples, respiratory secretions at day 14 were negative in only one patient. As a result, the high-dose arm of the study was prematurely halted.

GlobalData believes that the preliminary data from this Phase II study should not be used further for Covid-19 patients due to the QTc prolongation, as this can cause sudden death due to erratic heartbeats. CQ is an older treatment for malaria and its use for the coronavirus outbreak is currently being heavily debated. This study suggests that high-dose CQ does not meet the safety standards for treating Covid-19.

GlobalData believes any treatment for Covid-19 should not have side effects such a QTc prolongation, as the majority of Covid-19 patients already have a comorbidity and such an effect can be lethal. Although the enrolment for the high-dose CQ arm was halted due to the observed effects, the results for the low-dose arm have not yet been published. As such, it may be found to be safe and efficacious; however, more patients need to be enrolled in this arm for it to show significance. Until the full set of results for the low-dose CQ arm is published, it is unclear whether or not this drug is efficacious for Covid-19. However, the preliminary results have identified that the high dose is not to be used.

If the low dose is found to be efficacious, it would be a breakthrough for Covid-19 treatment. As the drug has been widely used already, GlobalData expects that it would be cheaper compared to a brand new therapy for coronavirus. This could potentially have significant economic benefits, as Covid-19 is a global pandemic and not all regions can afford premium-priced agents.