Vertex Pharmaceuticals (VRTX - Get Report) confirmed Tuesday the next generation of cystic fibrosis drugs from its research labs will begin mid-stage clinical trials by the end of the year.

Vertex is developing these drugs, VX-440 and VX-152, to become components of new combination regimens to treat the underlying cause of cystic fibrosis.

The company's hope is the new drugs will improve on the efficacy and tolerability of Orkambi, the first combination therapy approved for cystic fibrosis in 2015. Orkambi sales have helped Vertex turn profitable for the first time but the drug's commercial performance has also fallen short of Wall Street expectations because patients find the drug's benefit modest relative to its side effects.

Vertex is also looking over its shoulder as other drug companies, including AbbVie (ABBV - Get Report) and Galapagos (GLPG - Get Report) , try to develop competing cystic fibrosis therapies.

The phase II studies announced Tuesday will incorporate VX-440 and VX-152 into separate triple-combination regimens in cystic fibrosis patients with one copy of the F580del mutation and a minimal function mutation and also patients with two copies of the F508del mutation.

The phase II studies are expected to start enrolling patients before the end of the year with results -- safety and improvements in lung function -- announced in the second half of 2017. If positive, Vertex would move one or both of the new drugs into phase III studies.

Investors have been waiting months for Vertex to announce the new combination-therapy studies of VX-440 and VX-152 so the confirmation Tuesday was welcome news and overshadowed third-quarter financial results.

Vertex shares rose 7% to $84.10 in Tuesday after-hours trading. The stock closed the regular trading session at $78.71.

For the third quarter, Vertex reported adjusted earnings of 16 cents on total revenue of $414 million. Orkambi sales in the quarter were $234 million, in line with lowered consensus.

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