I've been trying to understand the ivermectin controversy (especially in view of NIH's recent [partial] change of heart). Based on one of the more recent papers (Jans & Wagstaff) which proposes ivermectin as an antiviral, there are 70+ clinical trials of ivermectin for Covid-19 ongoing.
But what strikes me as odd is that besides a few in vitro research papers mentioned, there's almost a complete dearth of mentions/citations of animal models where ivermectin was successfully used as an antiviral. Contrast this with almost any antiviral for which there are dozens of such animal studies, e.g. for a nearly random example see oseltamivir in this WHO review. So, for ivermectin, as an antiviral, it seems a jump straight from "the test tube" to people.... which seem very unusual, especially since Jans & Wagstaff acknowledge that dosing something as an antiviral is not trivial.
As in many other disciplines, one of the biggest challenges in antiviral research is to transition from laboratory experiments to preclinical/clinical studies, with the question of dosing in the case of ivermectin for viral infectious indications contentious [...]. It is important, firstly, to stress the obvious in this context: that the antiviral activities of ivermectin documented in Table 2 have been derived from laboratory experiments that largely involve high, generally non-physiological, multiplicities of infection, and cell monolayer cultures, often of cell lines such as Vero cells (African green monkey kidney cells impaired in interferon α/β production) that are not clinically relevant.
And then Jans & Wagstaff mention (just) one animal trial:
preclinical studies in a lethal Pseudorabies (PRV) mouse challenge model showed that dosing (0.2 mg/kg) 12 h post-infection protected 50% of mice, which could be increased to 60% through administration of ivermectin at the time of infection.
But maybe this paper is just not revealing the full breadth of animal studies for ivermectin as an antiviral, even though there are a lot more of them?