Anamorelin (ONO-7643): Clinical Overview for Providers

Anamorelin, developed as ONO-7643, is an orally active ghrelin receptor agonist developed specifically for cancer anorexia-cachexia syndrome rather than for elective use. Its development history is the most instructive in the secretagogue class, because it tested the central assumption behind the entire category and returned an uncomfortable answer.

This guide situates Anamorelin within the broader field of peptide therapy and is written for clinicians. It is clinical education, not medical advice, and nothing here should be read as a treatment recommendation or protocol.

What is anamorelin?

Anamorelin is a small non-peptide molecule that activates the growth hormone secretagogue receptor GHS-R1a. Like MK-677, it is orally active and is not itself a peptide, despite acting at a peptide hormone's receptor.

It was developed for a specific and serious indication: cancer anorexia-cachexia syndrome, the wasting that accompanies advanced malignancy and independently worsens survival and quality of life. This is not a cosmetic context. Cachexia is a genuine unmet need, and appetite stimulation plus anabolic signaling is a rational approach to it.

What the ROMANA trials showed

The pivotal ROMANA phase 3 program studied anamorelin in patients with advanced non-small cell lung cancer and cachexia. The results were split in a way that determined the drug's fate.

Anamorelin significantly increased lean body mass compared with placebo, along with improvements in body weight and some patient-reported anorexia symptoms. It did what it was designed to do to body composition.

It did not improve handgrip strength, the co-primary functional endpoint. The tissue was added; the function was not.

That divergence is the whole lesson. Regulators had required a functional co-primary endpoint precisely because lean mass on a scan is a surrogate, not a benefit a patient experiences. Anamorelin has been approved in Japan for cancer cachexia in specified settings, but it did not secure approval in the United States or Europe on this evidence.

Why lean mass and function diverge

The gap between mass and function recurs throughout this field. MK-677's two-year trial in older adults produced the same pattern: increased fat-free mass, no improvement in strength or physical function. Bimagrumab raises the same question from a different mechanism.

Several factors contribute. A portion of measured lean mass gain is fluid retention rather than contractile tissue. Muscle mass and muscle quality are not the same variable. And functional capacity depends on neuromuscular factors and on actually loading the muscle, which no pharmacologic agent supplies.

The practical translation is direct: an agent that adds mass without loading produces mass that does not work. This is the strongest argument for why resistance training is not an optional adjunct to anabolic pharmacology but the thing that makes it meaningful.

Regulatory status

Anamorelin is not FDA-approved in the United States. It has been approved in Japan for cancer cachexia within a defined indication.

It is not an elective body-composition agent and was never developed as one. Its relevance to general practice is as evidence rather than as therapy: it is the best-documented test of whether a ghrelin receptor agonist translates body composition change into functional benefit, and the answer it returned should inform how every agent in this class is discussed with patients.