# Hormone selectivity during redesign

> Route 66 Peptides weighs hormone selectivity — Route 66 Peptides compares acute ipamorelin hormone selectivity with the preclinical cortisol observation reported for its oral derivative NN703.

An altered route can come with altered pharmacology. The oral-development papers make that trade-off worth examining.

## The parent peptide

The [founding ipamorelin characterization](https://pubmed.ncbi.nlm.nih.gov/9849822/) tested rat pituitary cells, anaesthetised rats and conscious swine. It found potent growth-hormone release, while ACTH and cortisol remained at or below the response associated with growth-hormone-releasing hormone, even at doses more than 200-fold above the growth-hormone ED50.

That is a strikingly specific achievement. The word selective earns my respect in this acute hormonal experiment. The observation describes the measured hormone responses over the study's acute window; it leaves longer exposure and other outcomes to further work.

> The comparison was with growth-hormone-releasing hormone. The finding describes relative hormone responses in acute preclinical tests.

## The oral derivative

In the [animal characterization of NN703](https://pubmed.ncbi.nlm.nih.gov/10427162/), a structurally modified ipamorelin derivative achieved oral access in dogs. The characterization also reports a 50% cortisol increase at all tested doses, with no dose-dependent pattern. The derivative therefore warrants a separate hormonal assessment.

The experimental conditions and comparator would be essential before explaining why cortisol changed. Oral engineering leaves the derivative's hormonal profile as a question to investigate in its own right.

## Selectivity and safety

The parent peptide's [acute hormone result](https://pubmed.ncbi.nlm.nih.gov/9849822/) measured a particular kind of selectivity. A [review assessing ipamorelin among peptide therapies](https://pubmed.ncbi.nlm.nih.gov/41966639/) describes scarce rigorous human safety data and the potential for serious harm. That wider safety question remains open beyond the appealing hormone comparison.

I would celebrate a cleanly defined pharmacological advantage and still ask for a human safety record suited to the proposed use. The [human-studies page](/human-studies) shows the kinds of exposure and outcomes that were actually measured for intravenous ipamorelin.

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Route 66 Peptides is my roadside notebook of published research, an editorial project with no sales or medical advice.