Ghoul
Member
Different from serostim?
I have PBS on the way LOL
Reta is not FDA approved yet but quick search shows around pH 8
So the two types of aggregation that can occur are "growth", where peptides bump into each other and adhere into a "snowball" kind of structure, growing larger over time.
The other type of aggregation is spontaneous, where certain conditions will cause a certain size and shape to form almost immediately. with no intermediate "growth".
The latter is what I think the strings are, and most commonly the result of the PH being too acidic or base.
What may happen is the PH changes a little as the solution sits, just enough for the conditions to no longer support the spontaneous large...
7.4 is the most comfortable. since it matches human ph. "isotonic"
But depending on the protein involved. it may not be ideal for storage in reconstituted form.
rHGH is most stable when it's slightly acidic.
Commercial formulations include buffers to reach a particular PH after reconstitution, and some go closer to 7.4 for a more comfortable injection, but include other stabilizers to prevent aggregation for the inherently less stable conditions created by that higher PH. Serostim is the exception, a 30 year old formula, with a 7.4 target ph and no anti-aggregation excipients. On the other hand it's stored and shipped in temperature controlled conditions (below 86f), protected with nitrogen, so it's not damaged in any of the ways that promote aggregation (oxidation, heat).
A box near the top of a shipping container from China can hit 158f, so by the time it reaches us, it could be very susceptible to aggregation vs undamaged rHGH.
