This week, the overall grades of 13 Biotechnology stocks are lower, according to the Portfolio Grader database. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

This week, Regeneron Pharmaceuticals, Inc. (REGN) drops from a C to a D rating. Regeneron Pharmaceuticals, Inc. researches, develops and commercializes therapeutics to treat human disorders and conditions. The company also gets F’s in earnings surprise. For more information, get Portfolio Grader’s complete analysis of REGN stock.

Alexion Pharmaceuticals, Inc. (ALXN) slips from a C to a D this week. Alexion Pharmaceuticals, Inc. engages in the innovation, development, and commercialization of life-transforming therapeutic products for treating patients with severe and ultra-rare disorders in the United States, Europe, Latin America, Japan, and the Asia Pacific. The company also gets F’s in operating margin growth. For more information, get Portfolio Grader’s complete analysis of ALXN stock.

Gilead Sciences, Inc.’s (GILD) rating weakens this week, dropping to a D versus last week’s B. Gilead Sciences, Inc. is a research-based biopharmaceutical company that discovers, develops, and commercializes therapeutics to advance the care of patients suffering from life-threatening diseases. For more information, get Portfolio Grader’s complete analysis of GILD stock.

Slipping from a C to a D rating, Forward Pharma A/S Sponsored ADR (FWP) takes a hit this week. The company also gets F’s in return on equity. For more information, get Portfolio Grader’s complete analysis of FWP stock.

Insmed Incorporated (INSM) experiences a ratings drop this week, going from last week’s D to a F. Insmed Incorporated develops and commercializes drugs that treat metabolic diseases, endocrine disorders and oncology. The company also gets F’s in return on equity and free cash flow. For more information, get Portfolio Grader’s complete analysis of INSM stock.

This week, Halozyme Therapeutics, Inc.’s (HALO) rating worsens to a D from the company’s C rating a week ago. Halozyme Therapeutics, Inc. is a biopharmaceutical company developing products for the diabetes, cancer, dermatology and drug delivery markets. The company also gets F’s in earnings revisions and return on equity. For more information, get Portfolio Grader’s complete analysis of HALO stock.

This is a rough week for Flexion Therapeutics, Inc. (FLXN). The company’s rating falls to D from the previous week’s C. The company also gets F’s in earnings revisions, return on equity, and free cash flow. For more information, get Portfolio Grader’s complete analysis of FLXN stock.

Mesoblast Limited Sponsored ADR (MESO) declines this week from a C to a D. The company also gets F’s in earnings surprise, return on equity, and free cash flow. For more information, get Portfolio Grader’s complete analysis of MESO stock.

Exact Sciences Corporation (EXAS) earns a F this week, moving down from last week’s grade of D. 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.

Genocea Biosciences, Inc. (GNCA) gets weaker ratings this week as last week’s C drops to a D. The company also gets F’s in sales growth, return on equity, and free cash flow. For more information, get Portfolio Grader’s complete analysis of GNCA stock.

Nexvet Biopharma PLC (NVET) is having a tough week. The company’s rating falls from a D to a F. The company also gets F’s in earnings momentum, return on equity, and free cash flow. For more information, get Portfolio Grader’s complete analysis of NVET stock.

This is a rough week for ArQule, Inc. (ARQL). The company’s rating falls to D from the previous week’s C. ArQule, Inc. is a biotechnology company that is engaged in the research and development of cancer therapeutics. The company also gets F’s in return on equity. For more information, get Portfolio Grader’s complete analysis of ARQL stock.

IsoRay, Inc. (ISR) is having a tough week. The company’s rating falls from a C to a D. IsoRay, Inc. produces a brachytherapy seed, used to treat prostate and other cancers. The company also gets F’s in earnings revisions and return on equity. For more information, get Portfolio Grader’s complete analysis of ISR 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.