The overall ratings of three Biotechnology stocks are down on Portfolio Grader this week. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

Progenics Pharmaceuticals’ (NASDAQ:PGNX) rating falls to a D (“sell”) this week, down from C (“hold”) the week prior. Progenics Pharmaceuticals develops and distributes therapeutic products to treat the unmet medical needs of patients with debilitating conditions and life-threatening diseases. In Portfolio Grader’s specific subcategories of Earnings Momentum, Earnings Revisions, Equity, and Sales Growth, PGNX also gets F’s. For a full analysis of PGNX stock, visit Portfolio Grader.

The rating of Rigel Pharmaceuticals (NASDAQ:RIGL) declines this week from C to a D. Rigel Pharma discovers and develops novel, small molecule drugs in four lead product development programs: allergy/asthma, autoimmune disorders, hepatitis C, and cancer. The stock gets F’s in Equity, Cash Flow, and Sales Growth. The stock price has fallen 21.2% over the past month, worse than the 4.7% increase the Nasdaq has seen over the same period of time. To get an in-depth look at RIGL, get Portfolio Grader’s complete analysis of RIGL stock.

The rating of Ironwood Pharmaceuticals (NASDAQ:IRWD) slips from C to a D. Ironwood Pharmaceuticals discovers, develops, manufactures, and commercializes marketed drugs. The stock also gets an F in Equity. For more information, get Portfolio Grader’s complete analysis of IRWD 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.