Katcher specifically commented on this, saying that E5 was 'upstream' of GDF11.
Did he say this in a recent interview? I have not heard it from him, nor does he say so in his book.
E5 surely must be some combination of endogenous plasma signalling molecules like GDF11, Oxytocin, TIMP2, GnRH, Klotho, Humanin...
How else could Harold have come up with E5 in a short space of time before his Indian Visa expired, once he discovered they weren't able to perform a rat plasma exchange? Harold has proposed that a cell's age is guided by systemic factors, but he didn't do any of the actual work to discover what these factors might be himself - he got them from the literature, which we can all read.
For example in his 2015 paper he mentions the following:
Towards an Evidence-based Model of Aging
Other substances, the product of the GDF11 gene, the protein BMP-11 (a member of the bone morphogenetic protein family), has been shown
to return muscle satellite cells to youthful functioning [18], while oxytocin [56], has been shown to have similar effects on skeletal muscle. We know that several tissue clocks dependent on the SCN in the hypothalamus are dependent on gonadotrophin releasing factor, and that this affects lifespan [47], as re-provision of the ‘hormone’ increases lifespan. PMID: 26054348
In his book Harold states he carries out no dilution or removal of bad actors (like CCL-11, which he also mentions in his above paper), he just adds in good/'youthening' factors at a higher concentration than would normally be present in youthful plasma.
I like Harold and Akshay, who I've corresponded with before. But really, how are natural, endogenous substances patentable? I'm no expert on patent law, but I'd guess they'd have to patent the dose/timing/proprietary formulation. I doubt they'd be able to patent the 'use', i.e. aging, given they are going through the FDA, but I could be wrong. I also suspect that the exact combination of molecules in E5 will not be the only one that works, so others could find ways around any patent.
Sorry if this is a little off topic, but it is relevant to GDF11, and I'd thought I'd give my 2 pence!