Tesamorelin and Cancer Risk: What the Research Says
Unlike most «peptides» from the gray market, tesamorelin is a registered drug, so there is a regulator's label, randomized trial data, and long-term observations for it. This makes it possible to discuss cancer risks more concretely. The editorial team examined what the official documents and research say, and where blank spots remain.
Where the cancer concern comes from
Tesamorelin is an analog of growth-hormone-releasing hormone (GHRH). It stimulates the pituitary to release more growth hormone (GH), which leads to an increase in the level of insulin-like growth factor-1 (IGF-1). It is IGF-1 that is the main reason for cancer warnings about all drugs that activate this axis.
IGF-1 stimulates cell division and suppresses apoptosis through the intracellular PI3K/Akt and MAPK signaling pathways. A review by Pollak in Nature Reviews Cancer (2008) described how this signaling supports the growth and survival of tumor cells. Many types of cancer have IGF-1 receptors.
An epidemiological analysis by Renehan and colleagues (Lancet, 2004) showed that higher natural levels of IGF-1 are associated with a moderately increased risk of prostate cancer and premenopausal breast cancer. Although these are observational data, they shaped a general caution regarding a prolonged increase in IGF-1.
For tesamorelin an important distinction applies: the theoretical risk is associated not with the molecule itself, but with how much and for how long it raises IGF-1. That is precisely why the IGF-1 level is monitored in clinical use.
What is stated in the drug's label
The FDA label for tesamorelin (Egrifta) contains several provisions directly related to cancer risk. They are worth knowing for anyone interested in the drug, since they reflect the regulator's assessment based on the entire body of data.
- Contraindications:active malignant tumor — both newly diagnosed and recurrent.
- Prior tumors:in patients with a cancer history, the disease must be inactive before starting treatment, and antitumor treatment must be completed.
- Disorders of the hypothalamic-pituitary axis:conditions after hypophysectomy, pituitary tumors, head irradiation, and so on — are also contraindications.
- IGF-1 monitoring:it is recommended to periodically measure IGF-1 and to consider discontinuing treatment if values are persistently elevated.
- Background risk:the label separately reminds that in people with HIV the baseline risk of some malignancies is increased.
Such wording does not mean that the drug has been proven to cause cancer. It reflects the precautionary principle: given a plausible mechanism and incomplete long-term data, the regulator limits use in the groups where potential harm is greatest.
The label also emphasizes that the long-term effect of tesamorelin on cardiovascular outcomes has not been established, and that the drug is not intended for weight loss. This is a reminder that even a registered agent has a narrow indication.
For comparison: unregistered GHRH analogs, such as CJC-1295, have no such label at all, and therefore no formalized contraindications and monitoring rules.
Clinical trial data
The main evidence base for tesamorelin is two phase III trials in patients with HIV and excess abdominal fat, published by Falutz and colleagues (NEJM, 2007) and pooled in a 2010 analysis (JCEM) together with data from an extended safety phase. The total observation period in some participants reached a year.
In these trials the IGF-1 level naturally rose with tesamorelin. In some patients the values exceeded the upper limit of normal, which is what became the basis for the monitoring recommendation. No clear signal of an increase in the frequency of malignant tumors was reported in the randomized groups, but such a conclusion requires much longer and larger observations.
| Aspect | What is known | Limitation |
|---|---|---|
| IGF-1 level | Rises with treatment, in some patients above normal | Individual variability |
| Tumor frequency in RCTs | No clear signal was reported | Duration up to ~1 year, insufficient for cancer conclusions |
| Post-registration data | The drug has been in use since 2010 | Narrow population, limited volume |
| Off-label use | No systematic data | Unknown doses, duration, and monitoring |
Later studies — on liver fat (Stanley and colleagues, JAMA, 2014; Lancet HIV, 2019) and cognitive function in older people (Baker and colleagues, 2012) — also did not detect a cancer signal, but they were not designed to look for one.
It is important to understand the limits of these conclusions: they concern the defined doses, populations, and durations set by the protocols, with regular laboratory monitoring. Transferring the results to uncontrolled use, for example in sport, is incorrect.
Features of HIV patients
People living with HIV have a higher risk than the general population of a number of cancers — both related to immunodeficiency and unrelated. Modern antiretroviral therapy has significantly reduced the frequency of the most typical of them, but the question of cancer screening in this group remains relevant.
For assessing the safety of tesamorelin, this creates a methodological difficulty. Any case of cancer in a study has to be compared with an already elevated background risk, and the effect of the drug can be distinguished from the natural course only in comparison with a control group of sufficient size.
The practical conclusion that follows from the label: before prescribing tesamorelin, the doctor must assess the patient's cancer history and current condition, and during treatment must adhere to age-appropriate screening programs and monitor for alarming symptoms.
At the same time, the benefit of reducing visceral fat for this group also matters: visceral obesity is associated with metabolic disorders and liver damage. The decision about treatment is always a balance of benefits and risks, assessed by the doctor together with the patient.
How the risk is managed in practice
In clinical practice, cancer safety is ensured not by a single test but by a system of measures. The first level is patient selection: excluding active malignancies and disorders of the pituitary region in accordance with the contraindications.
The second level is regular measurement of IGF-1. The doctor compares the result with the laboratory's age norm and, if the value persistently exceeds it, reconsiders the appropriateness of continuing treatment. This approach is borrowed from the practice of growth hormone therapy.
The third level is assessment of effectiveness. If after a defined period the visceral fat has not significantly decreased, the label suggests considering discontinuation of therapy. Continuing treatment without benefit means exposing oneself to risks without compensation.
The fourth level is standard cancer screening according to age and risk factors. Tesamorelin does not cancel any recommendations regarding colonoscopy, mammography, or prostate examination.
Editorial conclusions
The cancer concern about tesamorelin follows from the biology of the GH/IGF-1 axis, not from a signal detected in studies. However, the duration of the available studies is insufficient to completely rule out risk.
The FDA label enshrines the precautionary principle: an active malignant tumor is a contraindication, and it is recommended to monitor IGF-1.
Off-label use without laboratory monitoring deprives a person of all these safeguards.
We also recommend reading «CJC-1295 and cancer risk: what the research says», «The history of the discovery of Tesamorelin», and «Tesamorelin and carbohydrate metabolism».
References
- EGRIFTA (tesamorelin for injection). Prescribing information. Theratechnologies Inc.; U.S. Food and Drug Administration.
- Falutz J, Allas S, Blot K, et al. Metabolic effects of a growth hormone-releasing factor in patients with HIV. N Engl J Med. 2007;357(23):2359–2370.
- Falutz J, Mamputu JC, Potvin D, et al. Effects of tesamorelin (TH9507), a growth hormone-releasing factor analog, in human immunodeficiency virus-infected patients with excess abdominal fat: a pooled analysis of two multicenter, double-blind placebo-controlled phase 3 trials with safety extension data. J Clin Endocrinol Metab. 2010;95(9):4291–4304.
- Renehan AG, Zwahlen M, Minder C, et al. Insulin-like growth factor (IGF)-I, IGF binding protein-3, and cancer risk: systematic review and meta-regression analysis. Lancet. 2004;363(9418):1346–1353.
- Pollak M. Insulin and insulin-like growth factor signalling in neoplasia. Nat Rev Cancer. 2008;8(12):915–928.
- Stanley TL, Feldpausch MN, Oh J, et al. Effect of tesamorelin on visceral fat and liver fat in HIV-infected patients with abdominal fat accumulation: a randomized clinical trial. JAMA. 2014;312(4):380–389.
- World Anti-Doping Agency. Prohibited List. Montreal: WADA; чинна редакція.
Andriy Melnyk
A strength-sports coach and author of programs for beginner and intermediate levels. Writes about training planning.
