The STEP UP and STEP UP T2D clinical trials are the first to investigate whether increasing the dose of semaglutide from the currently approved dose of 2·4 mg to 7·2 mg is safe and leads to additional weight reduction. Trial participants were randomized to receive either the higher 7·2 mg dose of semaglutide, the currently approved 2.4 mg dose, or placebo over 72 weeks. All participants -- regardless of treatment group -- received lifestyle interventions such as dietary counseling and increased physical activity recommendations.

In adults without diabetes, a 7·2 mg dose of semaglutide led to an average weight loss of nearly 19%, surpassing the 16% loss seen with 2·4 mg and 4% with placebo. Nearly half of the participants on the higher dose lost 20% or more of their body weight, with about one-third losing at least 25%. Participants also experienced improvements in waist circumference, blood pressure, blood sugar, and cholesterol levels, all key factors in reducing obesity-related health risks. Similarly, in adults with obesity and T2D, the 7·2 mg dose resulted in an average 13% weight loss compared to 10% with 2.4 mg and 3.9% with placebo, along with significant reductions in blood sugar levels and waist size.

Both trials reported that the higher dose of semaglutide was safe and generally well tolerated. Gastrointestinal side effects like nausea and diarrhea, and some sensory symptoms like tingling, were the most common. However, most side effects were manageable, resolved over time, and did not lead to participants dropping out of the trial. No increase in serious adverse events or severe hypoglycemia was observed with the higher dose.

By delivering greater weight reduction and metabolic benefits while maintaining a favorable safety profile, the authors say this higher dose could help more people reach their health goals and reduce the burden of obesity-related complications worldwide. However, they highlight that further research is needed to fully understand the long-term benefits and risks.

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This is the result of a study published in Science Advances, led by Francesco Cecconi, Full Professor of Biochemistry at the Department of Basic Biotechnological Sciences, Intensive Care and Perioperative Medicine at the Università Cattolica, and conducted by Valentina Cianfanelli, Associate Professor at the Department of Science at Roma Tre University and Principal Investigator of the Young Researchers Project at the Gynecological Oncology Unit of Fondazione Policlinico Universitario Agostino Gemelli IRCCS.

Background

Mitochondria are highly complex cellular organelles, vital for cell survival. They are responsible for producing the energy cells need to survive. Their integrity is associated with several diseases, both widespread, such as Parkinson's, and rare, so-called mitochondrial diseases, which can affect various parts of the body, from muscles to eyes to the brain. Inside cells, there is a delicate balance between old or damaged mitochondria that must be eliminated and new ones that must replace them. In some diseases, however, this balance is disrupted, and if mitochondria are lost in excess, or if damaged organelles accumulate in the cell and are regularly not eliminated, the very survival of the cell is endangered.

In the case of Parkinson's disease, for example, the loss of mitochondria also plays a role in the death of dopaminergic neurons that underlies the disease.

The Study

Experts have discovered that B55 plays a key role in regulating mitochondrial homeostasis.

"On the one hand," Professor Cecconi explains, "it promotes the removal of damaged mitochondria by stimulating mitophagy, a selective process for removing inefficient and potentially dangerous organelles. On the other, B55 acts as a controller of mitochondrial biogenesis, stabilizing the main promoter of new mitochondrial formation.

In this way, B55 not only promotes the degradation of damaged mitochondria, but also prevents excessive production of new organelles, thus maintaining a dynamic balance between mitochondrial elimination and synthesis. It is of great interest," the expert emphasizes, "that both these effects depend on the functional interaction between B55 and Parkin, a central protein in mitophagy mechanisms, implicated in Parkinson's disease.

Professor Cecconi and Cianfanelli explain: it is no coincidence that in our research, using animal models of Parkinson's disease (Drosophila, the fruit flies), "we observed that by reducing B55 levels we can improve both the motor defects and the mitochondrial alterations typical of the disease." This effect requires the presence of the Parkin factor and acts primarily on mitochondrial biogenesis.

The idea could be to develop small molecules capable of penetrating the brain and selectively acting on dopaminergic neurons, counteracting their death.

More generally, a 'universal' drug that regulates the action of B55 could be developed for various mitochondrial diseases characterized by mitochondrial loss, including some mitochondrial myopathies and neurodegenerative diseases, Professor Cecconi explains. Furthermore, the deregulation of mitochondrial quality and number also underlies the plasticity of tumor cells and their ability to resist therapies, so controlling B55 could become a promising approach in oncology.

This is why "our future studies will aim to identify safe molecules and therapeutic strategies to modulate B55 in preclinical and human cellular models, especially in order to analyze the effect of its regulation on other neurodegenerative and mitochondrial diseases," they conclude.