Egrifta (Tesamorelin) Side Effects: Delayed-Onset Adverse Events Explained

Does tesamorelin cause delayed side effects?

Tesamorelin is a synthetic analog of growth hormone-releasing factor, also called growth hormone-releasing hormone [1]. It binds GRF receptors on pituitary somatotroph cells and stimulates the pulsatile release of the body's own growth hormone, which raises IGF-1 and IGFBP-3 [1].

The label frames the long-horizon concern directly: it states that the effects of prolonged elevations in IGF-1 levels are unknown, and asks prescribers to monitor IGF-1 during therapy [1].

Two labels cover the drug today: Egrifta SV, a 2 mg vial given as 1.4 mg once daily, and Egrifta WR, an 11.6 mg vial given as 1.28 mg once daily [1][2]. The labels state the two are not substitutable [2]. Their safety sections rest on trials of the original 1 mg/vial product dosed at 2 mg daily, and each label states that reactions at its own dose are expected to be similar [1][2]. Neither label carries a boxed warning [1][2].

IGF-1: the clearest time-dependent effect

IGF-1 is the marker that rises with treatment, and the label reports it by treatment duration.

Among patients who received Egrifta for 26 weeks, 47% had IGF-1 levels above 2 standard deviation scores (SDS) and 36% were above 3 SDS, with the effect seen as early as 13 weeks of treatment [1]. Among patients who stayed on treatment to 52 weeks, 34% were above 2 SDS and 23% above 3 SDS at the end of treatment [1].

The label asks prescribers to monitor IGF-1 and to consider discontinuing in patients with persistent elevations, for example above 3 SDS, particularly when the reduction in visceral fat has not been robust [1].

Glucose and HbA1c: the week-26 finding

Mean baseline HbA1c was 5.3% in both the tesamorelin and placebo groups in the trials [1]. By week 26, 5% of tesamorelin-treated patients had an HbA1c of 6.5% or higher, against 1% on placebo, a hazard ratio of 3.3 (95% CI 1.4 to 9.6) [1].

The label tells prescribers to evaluate glucose status before starting and to monitor periodically to diagnose impaired glucose tolerance or diabetes [1]. It directs regular-interval monitoring of patients with diabetes for development or worsening of retinopathy, and says to consider discontinuing in patients who develop glucose intolerance or diabetes and do not show a clear efficacy response [1].

Fluid retention: edema, joint pain and carpal tunnel

The label groups these under one warning. Fluid retention, thought to be related to the induction of GH secretion, shows up as increased tissue turgor and musculoskeletal discomfort that produces edema, arthralgia and carpal tunnel syndrome, and the label describes these reactions as either transient or resolving with discontinuation of treatment [1].

Rates from the 26-week combined table: arthralgia 13% on tesamorelin versus 11% on placebo, peripheral edema 6% versus 2%, myalgia 6% versus 2%, pain in an extremity 6% versus 5%, paresthesia 5% versus 2%, hypoesthesia 4% versus 2%, and carpal tunnel syndrome 1% versus 0% [1]. Arthralgia, injection-site erythema, injection-site pruritus, pain in an extremity, peripheral edema and myalgia are the reactions reported in more than 5% of treated patients [1].

Injection-site reactions with daily injections

Egrifta SV is injected into the abdomen once daily, rotating sites and avoiding scar tissue, bruises and the navel [1]. Injection-site reactions occurred in 25% of tesamorelin-treated patients versus 14% on placebo during the first 26 weeks of the trials [1]. The label lists erythema, pruritus, pain, irritation and bruising, and states that rotating sites to different areas of the abdomen decreases them [1].

Hypersensitivity reactions and antibodies

Hypersensitivity reactions occurred in 4% of patients treated with Egrifta in clinical trials and included pruritus, erythema, flushing, urticaria and rash [1]. The label advises patients to seek prompt medical attention and stop treatment immediately if a hypersensitivity reaction is suspected [1].

Antibody data come from the original 1 mg/vial product. Anti-tesamorelin IgG antibodies were present in 50% of patients at 26 weeks and 47% at 52 weeks; 85% of patients with hypersensitivity reactions had antibodies; neutralizing antibodies were found in about 10% against tesamorelin and 5% against human GHRH at week 52 [1]. Fat loss and IGF-1 response were similar with or without antibodies [1].

What the label watches over longer periods

Neoplasms: tesamorelin induces release of growth hormone, a known growth factor. The label says any preexisting malignancy should be inactive with treatment complete before starting, and that tesamorelin should be discontinued if there is any evidence of recurrent malignancy [1]. Active malignancy is a contraindication [1].

Critical illness: increased mortality has been reported after treatment with pharmacologic amounts of growth hormone in patients with acute critical illness from open heart surgery, abdominal surgery, multiple accidental trauma or acute respiratory failure, and the label says to consider discontinuing tesamorelin in critically ill patients [1].

Long-term cardiovascular safety has not been established, and the label asks prescribers to consider the risk and benefit of continuing in patients who have not had a reduction in visceral adipose tissue [1].

Stopping also changes things over time. In the extension phase, patients switched from tesamorelin to placebo between weeks 26 and 52 had visceral fat changes of +16% to +22%, while those who continued had changes of about 0% to -5% [1].

What is not documented about timing

The Egrifta SV and Egrifta WR labels give no onset dates for edema, joint pain or carpal tunnel syndrome; the 26-week results show how often these reactions were reported, not when each began [1][2]. The FDA's adverse event dashboard includes reports from industry, healthcare professionals and consumers. Those reports cannot establish that a drug caused an event or show how often it occurs [3].