Dec 4 (Reuters) - The Centers for Medicare & Medicaid

Services on Wednesday said it had entered into agreements with

Vertex Pharmaceuticals ( VRTX ) and bluebird bio to

help increase patient access to their gene therapies.

The so-called "outcomes-based agreements" will tie payments

to whether the therapy improves health outcomes for patients who

receive these drugs and are enrolled in government-backed

Medicaid insurance plans.