This week, 5 Biotechnology stocks are improving their overall rating on Portfolio Grader. Each of these rates an “A” (“strong buy”) or “B” overall (“buy”).

Exelixis, Inc. (EXEL) boosts its rating from a B to a A this week. Exelixis, Inc. is a development-stage biotechnology company dedicated to the discovery and development of small-molecule therapeutics for the treatment of cancer and other serious diseases. The company also gets A’s in sales growth, earnings revisions, and earnings surprise. For more information, get Portfolio Grader’s complete analysis of EXEL stock.

ARIAD Pharmaceuticals, Inc. (ARIA) improves from a C to a B rating this week. ARIAD Pharmaceuticals, Inc. is an oncology company that focuses on the discovery, development, and commercialization of medicines for cancer patients. The company also gets A’s in sales growth, earnings revisions, and earnings momentum. For more information, get Portfolio Grader’s complete analysis of ARIA stock.

This week, Sinovac Biotech Ltd.’s (SVA) ratings are up from a C last week to a B. Sinovac Biotech Ltd. researches, develops, manufactures, and markets various vaccines, including flu vaccines and vaccines for Hepatitis A. For more information, get Portfolio Grader’s complete analysis of SVA stock.

This is a strong week for Rigel Pharmaceuticals, Inc. (RIGL). The company’s rating climbs to B from the previous week’s C. Rigel Pharmaceuticals, Inc. is a clinical-stage drug development company that discovers and develops novel, small-molecule drugs for the treatment of inflammatory and autoimmune diseases, as well as muscle disorders. The company also gets A’s in sales growth and earnings surprise. For more information, get Portfolio Grader’s complete analysis of RIGL stock.

The rating of Sophiris Bio Inc. (SPHS) moves up this week, rising from a B to a A. The company also gets A’s in earnings revisions. For more information, get Portfolio Grader’s complete analysis of SPHS 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.