This week, 4 Biotechnology stocks are worse, according to the Portfolio Graderdatabase. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

United Therapeutics Corporation (UTHR) earns a D this week, moving down from last week’s grade of C. United Therapeutics Corporation is a biotechnology company that develops and commercializes therapeutic products for patients with chronic and life-threatening diseases. The company also gets F’s in earnings surprise. For more information, get Portfolio Grader’s complete analysis of UTHR stock.

Enanta Pharmaceuticals, Inc. (ENTA) gets weaker ratings this week as last week’s C drops to a D. The company also gets F’s in sales growth, earnings growth, earnings revisions, earnings surprise, and earnings momentum. For more information, get Portfolio Grader’s complete analysis of ENTA stock.

Exact Sciences Corporation’s (EXAS) rating weakens this week, dropping to a D versus last week’s C. Exact Sciences Corporation is a molecular diagnostics company, focuses on developing a molecular diagnostic technology for the early detection and prevention of colorectal pre-cancer and cancer. The company also gets F’s in return on equity and free cash flow. For more information, get Portfolio Grader’s complete analysis of EXAS stock.

Kamada Ltd (KMDA) is having a tough week. The company’s rating falls from a C to a D. Kamada Ltd develops, produces, and markets specialty plasma therapeutics, specific and general immune globulins, and other prescribed medicines using chromatographic purification technology. The company also gets F’s in return on equity. For more information, get Portfolio Grader’s complete analysis of KMDA stock.

Louis Navellier’s proprietary Portfolio Grader stock ranking system assesses roughly 5,000 companies every week based on a number of fundamental and quantitative measures. Stocks are given a letter grade based on their results — with A being “strong buy,” and F being “strong sell.” Explore the tool here.