Paratek Pharmaceuticals' Nuzyra was designed to overcome the problem of resistance to tetracycline, an antibiotic widely used until recent years.

The company said the Food and Drug Administration approved Nuzyra for treating bacterial pneumonia and severe skin infections.

Paratek plans to launch the antibiotic early next year, initially for use in hospitals. It hasn't disclosed the price.

Boston-based Paratek estimates its drug could eventually treat nearly 900,000 hospitalized U.S. patients annually

About 2 million Americans get infections from antibiotic-resistant bacteria each year and 23,000 die, according to the Centers for Disease Control and Prevention.

Paratek tested Nuzyra against several types of bacteria that cause pneumonia and skin infections. The drug was more effective than two standard antibiotics given to patients in comparison groups, company testing showed.

Many antibiotics no longer work well, if at all, against some bacterial infections, due to their overuse in medicine and livestock production.

Paratek's drug, also known as omadacycline, is the first in a new class of antibiotics. It's an updated version of tetracycline, a 65-year-old antibiotic that was a workhorse against skin, respiratory and other infections until increasing resistance limited its use. Paratek created its drug by tweaking tetracycline to block two common ways bacteria use to resist it.

The FDA approved both an IV version and a daily pill that patients can switch to when they leave the hospital, the company said. It will eventually market the drug for patients treated at doctors' offices and clinics.

Last week, the U.S. Health and Human Services Department announced at the United Nations General Assembly a new global effort to fight antibiotic resistance and develop new treatments. The 106 initial participants included drugmakers, government agencies, medical groups and animal food producers.