Thymalin

Thymalin is not one peptide. It is a mix of peptides taken from the thymus ^[12]. The thymus is a gland in the chest that helps train the immune system. Researchers say two very short peptides in the mix may be its active parts ^[13].

It was first taken from animal tissue by a research group in Russia ^[14]. Doctors in Russia use it to support the immune system ^[16]. It is also spelled Timalin ^[15]. Thymulin and thymosin alpha-1 are different molecules, not Thymalin.

No drug approved in the US contains it ^[1].

Thymalin has no approved use in the US: in 2024, FDA said Thymalin products sold online are new drugs with no approved application ^[1]. That means no Thymalin product may be sold as a drug. It does not mean FDA found it harmful; FDA has not reviewed it ^[1]. Its use in Russia does not change its US status. Checked 26 October 2026.

FDA also said those products were misbranded. Their labels could not give directions a person could follow without a doctor ^[1]. A label that says "research chemicals only" does not change this, FDA said ^[1].

A pharmacy may make a drug from a bulk substance only in certain cases. One case is a substance on a list FDA keeps under section 503A of the law ^[3]. FDA's list of nominated substances, updated in May 2026, does not name Thymalin ^[2]. It names thymulin, a different molecule ^[2].

The evidence grade is limited-human: studies in people report gains, but most are small, old or poorly described, and the ones that name a place were run in Russia and Ukraine ^{[5] [6] [7] [8]}.

People: in a 2003 study, 266 older people were followed. Some got Thymalin, a pineal extract called Epithalamin, or both, for the first 2 to 3 years ^[5]. Over 6 to 8 years, fewer people died in the treated groups than in the control group, the authors report ^[5]. The study came from the group that developed Thymalin, and its summary does not say how people were put in groups ^{[5] [14]}. In a 2021 report, patients with COVID-19 got Thymalin on top of usual care ^[6]. Blood signs of swelling and clotting fell faster ^[6]. In 60 patients with lung tuberculosis, adding Thymalin to drugs shortened hospital stays, a 1990 report says ^[7]. In 15 people with parkinsonism, a movement disorder, symptoms got better after a course of Thymalin ^[8]. That study compared people only with themselves, before and after ^[8].

Animals: in rats with a transplanted tumor, Thymalin stopped or shrank the tumor in more than half ^[9]. In rats with a hole in the jaw bone, Thymalin shots given with a bone graft helped the bone heal ^[10]. In old mice, it changed the mix of cells in bone marrow ^[11].

Cells: in human stem cells in a lab, Thymalin pushed cells toward mature immune cells ^[12]. In other lab tests, it lowered signals of swelling made by human blood cells ^{[13] [14]}. These are animal and lab results, not results in people.

No approved drug in the US contains Thymalin, and FDA calls the products sold online unapproved new drugs ^[1]. The federal list of substances pharmacies may use does not name it ^{[2] [3]}. There is no legal route to Thymalin in the US today.

Any open trial would appear in the trials block below, with the date the official registry was last checked.

One way of getting Thymalin shows up in federal records: websites that sell it as a research chemical ^[1]. In 2024, FDA sent a warning letter to an online seller that offered Thymalin along with two weight-loss drugs ^[1].

The seller's labels said the products were for research only and not for people ^[1]. FDA said the website showed they were meant for people, so they are drugs ^[1]. FDA said the Thymalin product had no approval and was misbranded ^[1]. FDA was especially concerned that the seller marketed it for children ^[1].

A law firm reports that FDA has stepped up action against peptides labeled for research use only ^[4].