I stand corrected on convalescent plasma therapy

1. Sorry I haven't been blogging these days. Mainly for personal reasons that have led me to feeling quite burned out over the last year or so. And I'm afraid I don't expect to resume posting any time soon. This is just a one-off post in order to say something that I should say: mea culpa!

In the past, I touted convalescent plasma therapy as a viable "band-aid" to deal with SARS-CoV-2/COVID-19 until a vaccine was ready. However, I stand corrected about this. Convalescent plasma therapy doesn't really work for COVID-19. That's the main take away or bottom line if you don't wish to read further.

2. So please no need to read further if you don't wish, but here are more details in case you do:

My mea culpa is based on the recently published "PLACID trial". Its accompanying editorial is worth a read too. The PLACID trial involved 464 patients in 39 public and private hospitals across India (randomized, but not blinded): 235 patients received the convalescent plasma, while 229 did not (placebo). The study looked at two endpoints - a P/F ratio below 100 or death. All that's necessary to know is P/F ratio indicates low oxygen in the blood aka hypoxemia. (A normal P/F ratio is 400-500. A P/F ratio 100 or less is very impaired, to say the least. P/F stands for PaO2/FiO2, that is, the ratio of arterial oxygen partial pressure to fraction of inspired oxygen. It's also called the Horowitz index.) The study found the 235 patients in the convalescent plasma arm had a 19% chance of reaching a P/F ratio 100 or less or death, while the 229 patients in the placebo arm had an 18% chance of reaching the same endpoints. There's no statistically significant difference between 19% and 18% in this trial.

3. All that said, it's interesting to note the following from the editorial: "convalescent plasma did exactly what the investigators hoped it would do, yet there was no net clinical benefit to patients". It seems the reason may be because, on the one hand, the convalescent plasma is successfully neutralizing the SARS-2 coronavirus (via antibodies), but on the other hand, the convalescent plasma is making the patient's blood more easily able to form blood clots aka thrombi (via clotting factors). And COVID-19 itself is (as the editorial notes) "a life threatening thrombotic disorder".

As such, a potential way forward may be to keep the antibodies, but eliminate the clotting factors. In short: monoclonal antibodies.

4. Finally, a vaccine might be on the way soon - still a surprise to me how fast vaccines are being developed! - which, if so, might diminish the priority to further research other therapies including monoclonal antibodies. In any case, see what pharma companies AstraZeneca and Johnson & Johnson have been saying, for example.