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FDA approves first rapid-acting insulin biosimilar

Merilog works like NovoLog to help control blood sugar when injected five to ten minutes before meals
Jennifer Larson writer headshot
By | Feb. 21, 2025 Medically reviewed by Karen Berger, Pharm.D.
FDA stamp - Merilog

Key takeaways

  • The U.S. Food and Drug Administration approved Merilog (insulin-aspart-szjj) for glycemic control in both adults and children with diabetes.

  • It is the first rapid-acting insulin biosimilar for NovoLog (insulin-aspart).

  • Merilog should be injected under the skin about five to ten minutes before mealtime.

In this article:

People with diabetes who need to use insulin now have another option to help manage blood sugar levels. The U.S. Food and Drug Administration (FDA) approved Merilog (insulin-aspart-szjj) to improve glycemic control in adults and children with diabetes. 

It’s the first rapid-acting insulin product that is a biosimilar for NovoLog (insulin-aspart).

Manufactured by Sanofi, Merilog joins two long-acting insulin biosimilar products that were approved by the FDA in 2021: Rezvoglar (insulin glargine-aglr) and Semglee (insulin glargine-yfgn).

“For the millions of people who rely on daily injections of insulin for treatment of diabetes, having a biosimilar option for their rapid-acting insulin injection can truly make a difference, as biosimilar products have the potential to increase access to these life-saving medications,” Dr. Sarah Yim, MD, director of the Office of Therapeutic Biologics and Biosimilars in the FDA’s Center for Drug Evaluation and Research, said in a statement. 

How Merilog works

According to the FDA, about 8.4 million people in the U.S. use insulin to help manage diabetes. For people with this condition, the pancreas doesn’t make enough of this particular hormone to help move sugar from the bloodstream into the cells, where it can be used for energy. As a result, the levels of glucose in the bloodstream stay high, which can damage blood vessels and nerves over time—and lead to other serious health conditions. 

Merilog is a fast-acting or rapid-acting insulin that replaces the insulin the body does not produce. It is injected under the skin about five to ten minutes before eating a meal and starts working about 15 minutes later. The effect will peak about an hour or two after injection and last about two to four hours. 

Merilog will be available in two forms: a 10 mL multi-dose vial and a 3 mL single-patient-use prefilled pen. The pen dials in one-unit increments, allowing you to customize the amount of rapid-acting insulin you need, taking into account factors such as physical activity or changes in mealtime. 

Appropriate injection sites for Merilog include the upper arm, the abdominal area, the thigh, or the buttocks. However, it’s important to rotate the injection site so that you don’t inject into the same location every single time. 

What are biosimilars?

Biosimilars are medications that the FDA considers to be highly similar, with no major clinical differences, to another biological product that is already approved. The original is often called the reference product. In this case, Merilog functions like Novo Nordisk’s NovoLog, which is the reference product. Manufacturers must prove that biosimilars are just as safe and effective as their reference products–and can be given at the same dosage. 

As with generic drugs, when biosimilar products are approved, there is more competition in the market, which can help drive down prices. Typically, biosimilars cost less than the original product. One study reported, “Prices for biosimilars are typically 15% to 35% lower than their respective brand-name reference biologic and can prompt the brand-name manufacturers to lower prices or offer discounts.”

What are the side effects of Merilog?

Some potential adverse reactions can occur when taking an insulin aspart product like Merilog, which can include:

  • Hypoglycemia (low blood sugar)
  • Allergic reactions 
  • Hypokalemia (low potassium levels)
  • Local injection site reactions
  • Lipodystrophy (disproportionate distribution of fat at the injection site)
  • Rash
  • Pruritus (itching)
  • Weight gain
  • Swelling of the hands and feet

It’s not safe to use a rapid-acting insulin product if your blood sugar is too low. People with diabetes who need to use insulin should discuss the benefits and risks of taking Merilog with their healthcare provider.

When will Merilog be available?

Merilog is expected to hit U.S. pharmacy shelves in July 2025.

How much will Merilog cost?

Sanofi, the manufacturer of Merilog, caps the cost of other insulin products at $35 for a 30-day supply, regardless of income, and whether you have insurance or not. The same price assurance may apply to Merilog, though costs have not yet been announced.