Tissue hydrolysate

Cerebroprotein hydrolysate is a mixture of low-molecular-weight peptides and amino acids made by enzymatic digestion of pig brain - the same class of product as Cerebrolysin, with which it is used interchangeably in much of the literature. It is licensed and widely prescribed in parts of Asia, Eastern Europe and Latin America for stroke and dementia, and it has been assessed repeatedly by Cochrane. The conclusions are consistent and unflattering. For acute ischaemic stroke: across seven RCTs and 1773 participants, no effect on death, and moderate-certainty evidence of an increase in non-fatal serious adverse events (RR 2.39, 95% CI 1.10-5.23). For vascular dementia: cognition and global function improved, but on very low-quality evidence throughout.

Thymalin is a polypeptide extract of calf thymus, made in St Petersburg from the 1970s and the thymic half of Vladimir Khavinson's bioregulator programme - epitalon's parent extract Epithalamin being the pineal half. Its most striking claim is also its most-cited paper: a controlled study in elderly people reporting that mortality fell 2.0-2.1-fold in the Thymalin group, and 4.1-fold in those given Thymalin with Epithalamin annually for six years. That is an extraordinary result, published in a journal with limited reach, from the group that developed the compound, and never independently replicated. It is not a defined molecule: it is a tissue hydrolysate whose composition is set by a manufacturing process, and the dipeptides KE and EW have since been identified within it.