Novo Nordisk's shares fell 5% in premarket trading on Monday after the firm warned that a key obesity medicine might be unavailable in the United States owing to supplier concerns.

Following difficulties with Good Manufacturing Practices, the business started a contract manufacturer filling syringes for its Wegovy pens for the US market has temporarily halted production and delivery.Novo Nordisk | 2021 World's Best Workplaces | Fortune

Wego was proving to be a profitable venture for the company at a time when its core insulin business was under price competition. The news is a setback for Novo Nordisk, which had hoped to establish the medicine in the obese market before a competitor drug from Eli Lilly was slated to launch in 2024.

Because of reduced prices and a decline in insulin sales volumes in China, the business stated last month that it expected sales growth to slow by around 3% in 2022. It does not expect supply constraints to have an impact on the previously stated expectation for 2021.

According to the Danish company, it does not expect to be able to match demand in the United States in the first half of 2022, and only a small number of new patients will be allowed to begin therapy. In the second half of 2022, it hopes to be able to meet demand in the United States.

Novo Nordisk declined to name the manufacturer but stated the problems were with a prominent international company's European site. The two parties are in talks, according to Reuters, and the firm believes the contractor has a "strong plan in place."

On February 2, the corporation will announce its full-year earnings.