By Ransdell Pierson

Aug 1 (Reuters) - Express Scripts Holding Co said on Monday it would add a handful of medicines in 2017 to its list of drugs that are excluded from insurance coverage, including treatments for arthritis and psoriasis, while several other medicines will be removed from the exclusion list.

The nation's largest pharmacy benefit manager has been excluding medicines from its coverage list since 2014, citing concern about costs to its health insurers and corporate customers. The 2017 excluded medicines list will entail 85 drugs, it said, compared with 87 in 2016.

By excluding drugs from its formulary, Express Scripts said it has been better able to negotiate lower prices from drugmakers, and will thereby save customers an estimated $1.8 billion in 2017, up from $1.3 billion this year. The coverage list determines whether millions of people with private insurance can easily use an insurance co-pay to buy their medicine.

The drugs that will be newly excluded in 2017 include Zyclara, a skin cream for actinic keratosis sold by Valeant Pharmaceuticals International Inc, a Canadian drugmaker that has been criticized for big price increases on its products. The condition involves scaly skin growths that can develop into skin cancer.

Express Scripts spokesman David Whitrap declined to comment whether Zyclara, which costs more than $1,100 a tube, or other specific drugs, have been excluded because of price hikes.

Other drugs that will be newly excluded from coverage next year include Bristol-Myers Squibb Co's arthritis treatment Orencia, Eli Lilly and Co's new Taltz treatment for psoriasis and brands of gout drug colchicine sold by privately held Prasco Laboratories and West Ward Pharmaceuticals Corp, a unit of Hikma.

Express Scripts said a number of drugs excluded in 2016 will no longer be excluded next year, including Pfizer Inc's arthritis drugs Xeljanz and Xeljanz XR and GlaxoSmithKline Plc's Arnuity Ellipta and Flovent Diskus asthma treatments.

All four of the drugs will instead be considered "preferred alternatives," following price negotiations between the drugmakers and Express Scripts. Whitrap declined to say what magnitude or price rebates his company may have won.

Two costly drugs for hepatitis C from Gilead Sciences Inc , Epclusa and Harvoni, remain on the 2016 excluded medications list, Whitrap said. But he said their status could change in 2017, with an announcement to be made later this year.

(Reporting by Ransdell Pierson; Editing by Bernard Orr)