# The dog experiments

> Oral analogues | Route 66 Peptides — Route 66 Peptides follows ipamorelin-derived oral candidates through dog absorption experiments and the separate tests of growth-hormone release.

The percentage reaching blood has a chemical identity attached to it. The oral studies reward a closer look at which candidate made the journey.

## An ipamorelin-derived series

In the [series of orally active growth-hormone secretagogues](https://pubmed.ncbi.nlm.nih.gov/9733496/), derivatives of the ipamorelin design achieved 10–55% oral bioavailability in dogs. A secretagogue stimulates hormone release. The same research program evaluated growth-hormone-releasing potency in rat pituitary cells and intravenously in swine.

Those are different experimental jobs. The dog measurements concern access to circulation after oral administration; the cell and swine tests concern a hormone response. I appreciate this division of labour. It leaves room to ask whether a structural change improves access, activity, or both, without assuming that one measurement answers everything.

> An oral absorption measurement in a dog and an intravenous potency measurement in a pig describe different parts of development.

![A beagle walking beside an animal-care technician in a spacious research-care room](images/dog-absorption-study.webp)

*An imagined animal-care scene accompanying the dog absorption studies; this is an editorial illustration, not a record of an experiment.*

## A second job for the stomach

A [rat experiment with radiolabelled GHRP-6 and NN703](https://pubmed.ncbi.nlm.nih.gov/11322495/) found that both compounds accumulated in the glandular stomach lining after intravenous administration. Gastric resection reduced the growth-hormone response to GHRP-6 by 60–70%, while the response to growth-hormone-releasing hormone was preserved. The resection result concerns GHRP-6.

The stomach had occupied a simple place in my imagination: an obstacle an oral candidate had to cross. This experiment gives it a more active role in the hormone story. The authors proposed that growth-hormone-releasing peptides partly act by triggering endogenous ghrelin secretion. It is a proposed mechanism from rat work, and NN703's presence in the tracer experiment deserves to stay separate from the GHRP-6 resection result.

## NN703 in beagle dogs

The [NN703 characterization](https://pubmed.ncbi.nlm.nih.gov/10427162/) reports 30% oral bioavailability and a plasma half-life of 4.1 ± 0.4 hours in beagle dogs. NN703 was structurally derived from ipamorelin for oral activity. That is an unusually concrete stop along the route: a named derivative, a species and a measurement of how long it remained in plasma.

I am satisfied calling that an absorption achievement. Extending the same satisfaction to lasting benefit would require another experiment. The [cortisol finding](/hormone-selectivity) in this characterization also gives the derivative a profile of its own.

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