Tesamorelin: the only FDA-approved peptide in our five — what that changes, and doesn't.
Tesamorelin is a synthetic analog of human growth hormone-releasing hormone (hGHRH), FDA-approved in 2010 under the brand Egrifta for reduction of excess abdominal fat in HIV-infected patients with lipodystrophy. It's the one peptide in our flagship five where the approved label, the published pivotal trials, and the pharmacokinetics are all on the public record.
- Trans-3-hexenoic acid-modified hGHRH(1-44) analog. Resists DPP-4 degradation; plasma half-life 26–38 min (SC).
- Approved dose: 2 mg subcutaneous daily (abdominal injection site).
- Pivotal trials (Falutz et al., NEJM 2007; Stanley et al., JAMA 2014) showed 15–18% visceral adipose tissue (VAT) reduction at 26 weeks.
- Works by stimulating endogenous GH pulses rather than supplying exogenous GH — so IGF-1 rises are modest and physiologic.
- US list price for Egrifta SV (branded): ~$3,200/month. Research-chemical vendor pricing: ~$60–$120 per 2 mg vial.
- Contraindicated in active malignancy, pituitary axis disruption, and pregnancy. Hypersensitivity reactions reported.
What tesamorelin is, structurally
Endogenous human GHRH is a 44-amino-acid peptide released from the hypothalamus that stimulates GH secretion from anterior pituitary somatotrophs. Its N-terminus is its business end — the first 29 residues retain most of the biological activity. Its problem is DPP-4 (dipeptidyl peptidase-4), which cleaves the second amino acid off the N-terminus and inactivates the peptide within minutes.
Tesamorelin is the full 44-aa GHRH with a trans-3-hexenoic acid group attached at the N-terminal tyrosine. That simple modification blocks DPP-4 cleavage, extends plasma half-life from ~7 minutes (native hGHRH) to ~26–38 minutes, and preserves receptor affinity at the pituitary GHRH receptor.
What the pivotal trials actually showed
Two 26-week Phase III trials (M-1 and M-2) randomized patients with HIV-associated lipodystrophy to tesamorelin 2 mg/day SC vs placebo. Primary endpoint was change in visceral adipose tissue by CT. Pooled results across the two trials:
- VAT reduction: ~15.2% (tesamorelin) vs +5% (placebo) at week 26.
- Trunk fat: reduced ~8%. Limb fat: not significantly changed — so not a generalized lipolytic.
- IGF-1 rose from baseline by a mean of ~80 µg/L, staying within physiologic range in most subjects.
- Fasting glucose: small increases (1–3 mg/dL) that did not meet significance for new-onset diabetes vs placebo.
- Triglycerides and non-HDL cholesterol: modest favorable changes.
Follow-up analyses (Stanley et al., 2014; JAMA) showed that tesamorelin also reduced hepatic steatosis in HIV patients, with liver fat fraction dropping by ~35% in responders over 6 months. This is the most interesting finding outside the label indication and has driven off-label interest in NAFLD research.
Pharmacokinetics, stripped down
| Parameter | Value | Source |
|---|---|---|
| Route | Subcutaneous (abdomen) | FDA label |
| Dose | 2 mg/day | FDA label |
| Cmax (single dose) | ~3,800 pg/mL | Label PK table |
| Tmax | ~0.15 hr (9 min) | Label PK table |
| Half-life | 26–38 min | Label PK table |
| Clearance | ~100 L/h in HIV-lipodystrophy patients | Label PK table |
| Metabolism | Proteolytic. No CYP involvement. | Label |
The short half-life is by design. Tesamorelin triggers a pulse of endogenous GH, the GH pulse triggers IGF-1 production over ~24 hours, and the system resets. Daily dosing matches this rhythm. Twice-daily dosing is not supported by the label PK and would not meaningfully increase IGF-1 response.
"Off-label" and research-chemical use — the gap
Branded Egrifta SV requires a prescription and is expensive. Research-chemical vendors sell tesamorelin at a small fraction of the branded price as an RUO compound. The compounds are chemically the same molecule; the meaningful differences are:
- Sterility assurance. Branded Egrifta is manufactured under cGMP with terminal sterility testing. RUO vials are typically produced at lower QC standards.
- Lot-level COA. Branded product has batch release testing; RUO vendors vary wildly on COA quality.
- Legal framework. Branded product is a prescription drug. RUO tesamorelin is a research chemical and is not for human consumption.
Safety signals worth knowing
- Hypersensitivity. Injection-site reactions (erythema, pruritus, pain) are the most common AE in the pivotal trials — ~25% of patients.
- Fluid retention / arthralgia. Classic GH-axis effects. Less common than with exogenous GH because tesamorelin respects negative feedback.
- Carpal tunnel symptoms. Reported, consistent with GH-axis activation.
- Glucose tolerance. Monitor if baseline dysglycemia is present; transient rises in fasting glucose are seen.
- Contraindications. Active malignancy. Pituitary disorders. Pregnancy. Concomitant corticosteroid therapy at doses that suppress the GH axis.
Reconstitution math (5 mg RUO vial)
| BAC water added | Concentration | Per IU (U-100) | For 2 mg dose |
|---|---|---|---|
| 1 mL | 5,000 mcg/mL | 50 mcg | 40 IU |
| 2 mL | 2,500 mcg/mL | 25 mcg | 80 IU (exceeds syringe) |
Note the label dose is 2 mg (= 2,000 mcg), which is larger than most research-vial sizing contemplates. Researchers using RUO tesamorelin typically have 5 mg vials and reconstitute with 1 mL; 40 IU on a U-100 syringe = 0.4 mL = 2,000 mcg.
Where to read further
- Falutz J, et al. "Metabolic effects of a growth hormone-releasing factor in patients with HIV." N. Engl. J. Med. 2007;357:2359–70.
- Stanley TL, et al. "Reduction in visceral adiposity is associated with an improved metabolic profile in HIV-infected patients receiving tesamorelin." Clin. Infect. Dis. 2012;54(11):1642–51.
- Stanley TL, et al. "Effects of tesamorelin on hepatic fat and visceral fat in HIV-infected patients." JAMA 2014;312(4):380–9.
- FDA. Egrifta SV (tesamorelin for injection) prescribing information, current revision.