This week, seven biotechnology stocks are improving their overall ratings on Portfolio Grader. Each of these stocks is rated an “A” (“strong buy”) or “B” overall (“buy”).

Northwest Biotherapeutics, Inc. (NWBO) is making progress this week as its rating of C (“hold”) from last week increases to a B (“buy”) rating this week. Northwest Biotherapeutics engages in discovering, developing, and commercializing immunotherapy products to treat cancers in the United States. In Portfolio Grader’s specific subcategories of Earnings Momentum and Sales Growth, NWBO also gets A’s. For more information, get Portfolio Grader’s complete analysis of NWBO stock.

This is a strong week for Pharmacyclics, Inc. (PCYC). The company’s rating climbs to B from the previous week’s C. Pharmacyclics is a pharmaceutical company developing products to improve upon current therapeutic approaches to cancer, atherosclerosis, and retinal disease. Shares of PCYC have increased 5% over the past month, better than the 1.3% decrease the Nasdaq has seen over the same period of time. For more information, get Portfolio Grader’s complete analysis of PCYC stock.

Acorda Therapeutics, Inc. (ACOR) improves from a C to a B rating this week. Acorda Therapeutics is a commercial stage biopharmaceutical company dedicated to the identification, development and commercialization of novel therapies that improve neurological function in people with multiple sclerosis (MS), spinal cord injury and other disorders of the central nervous system. For more information, get Portfolio Grader’s complete analysis of ACOR stock.

This week, Stemline Therapeutics, Inc. (STML) is making solid headway. The company’s rating improves to an A (“strong buy”) from last week’s B (“buy”) rating. For more information, get Portfolio Grader’s complete analysis of STML stock.

This week, Seattle Genetics, Inc. (SGEN) pushes up from a C to a B rating. Seattle Genetics is a clinical-stage biotechnology company that is focused on the development and commercialization of monoclonal antibody-based therapies for the treatment of cancer and autoimmune disease. For more information, get Portfolio Grader’s complete analysis of SGEN stock.

Amgen (AMGN) boosts its rating from a B to an A this week. Amgen discovers, develops, manufactures, and markets medicines for serious illnesses. At present, the stock has a dividend yield of 2.4%. For more information, get Portfolio Grader’s complete analysis of AMGN stock.

BioMarin Pharmaceutical (BMRN) shows solid improvement this week. The company’s rating rises from a C to a B. BioMarin Pharmaceutical develops and commercializes innovative pharmaceuticals for serious diseases and medical conditions. For more information, get Portfolio Grader’s complete analysis of BMRN 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.