Cempra Pharmaceuticals expects the offering price for its planned IPO to be between $11 and $13, the Chapel Hill company reported in a regulatory filing last week.

The company, which filed to go public in October, hopes to raise nearly $90 million through the offering. Cempra plans to sell 6 million shares, with underwriters of the offering having the option to buy up to 900,000 additional shares.

Cempra is developing treatments for drug-resistant skin infections and pneumonia. The company has two antibiotics in clinical trials.

One targets patients with pneumonia. The other is being tested as a treatment for skin infections, including methicillin-resistant Staphylococcus aureus, or MRSA.

The company's founder and CEO, Prabhavathi Fernandes, was involved in developing clarithromycin, a popular antibiotic used for sinus infections, bronchitis and pneumonia.

Cempra, which has 15 employees, has raised nearly $80 million since it was founded in 2006. It is one of several health care-related Triangle companies planning to go public.

Argos Therapeutics, a Durham company developing experimental medicines to treat kidney cancer, HIV and lupus, filed plans to raise as much as $86.3 million in an IPO. Lipo Science, a Raleigh company that sells a blood test to check risk of heart disease, also filed plans.