This matches what I've read, too. It's less about the virus during the later stages and more about the infected person's immune system. If they've entered a state of amplified immune response, colloquially called a "cytokine storm," organs are damaged when their cells are mistakenly attacked.
If you can moderate the immune system's reaction you can prevent significant damage. HCQ is useful for this type of immuno-suppression.
Here's a pre-print of an article from a few years back which talks about HCQ and cytokine storms:
Scott W. Canna, Edward M. Behrens. Making Sense of the Cytokine Storm: a conceptual framework for understanding, diagnosing and treating hemophagocytic syndromes. Pediatric Clinics of North America [Preprint]. April 2012.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3368378/
My understanding is that tocilizumab is roughly 100 times as expensive as hydroxychloroquine and has intensive storage requirements. I don't see how the drug scales.
If you can moderate the immune system's reaction you can prevent significant damage. HCQ is useful for this type of immuno-suppression.
Here's a pre-print of an article from a few years back which talks about HCQ and cytokine storms:
Scott W. Canna, Edward M. Behrens. Making Sense of the Cytokine Storm: a conceptual framework for understanding, diagnosing and treating hemophagocytic syndromes. Pediatric Clinics of North America [Preprint]. April 2012. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3368378/
Published article link: https://dx.doi.org/10.1016%2Fj.pcl.2012.03.002