The overall ratings of 16 Biotechnology stocks are down on Portfolio Grader this week. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

This week, bluebird bio, Inc.’s (BLUE) rating worsens to a D from the company’s B rating a week ago. The company also gets F’s in sales growth, earnings momentum, and return on equity. For more information, get Portfolio Grader’s complete analysis of BLUE stock.

Agios Pharmaceuticals, Inc. (AGIO) declines this week from a D to a F. The company also gets F’s in sales growth, earnings growth, earnings revisions, earnings momentum, and return on equity. For more information, get Portfolio Grader’s complete analysis of AGIO stock.

Slipping from a C to a D rating, TG Therapeutics, Inc. (TGTX) takes a hit this week. TG Therapeutics, Inc. is a clinical-stage biopharmaceutical company focused on the acquisition, development and commercialization of innovative pharmaceutical products for the treatment of cancer and other underserved therapeutic needs. The company also gets F’s in earnings surprise and return on equity. For more information, get Portfolio Grader’s complete analysis of TGTX stock.

ADMA Biologics, Inc. (ADMA) experiences a ratings drop this week, going from last week’s C to a D. The company also gets F’s in return on equity and free cash flow. For more information, get Portfolio Grader’s complete analysis of ADMA stock.

This week, Sangamo BioSciences, Inc. (SGMO) drops from a C to a D rating. Sangamo BioSciences, Inc. is engaged in the research, development and commercialization of novel transcription factors for gene regulation and gene modification. The company also gets F’s in sales growth, earnings surprise, and return on equity. For more information, get Portfolio Grader’s complete analysis of SGMO stock.

Merrimack Pharmaceuticals, Inc.’s (MACK) rating weakens this week, dropping to a D versus last week’s C. Merrimack Pharmaceuticals, Inc. is focused on the discovery, development and commercialization of drugs for the treatment of immunological and autoimmune diseases with an initial focus on cancer. The company also gets F’s in sales growth. For more information, get Portfolio Grader’s complete analysis of MACK stock.

Xenon Pharmaceuticals Inc. (XENE) earns a F this week, moving down from last week’s grade of D. The company also gets F’s in sales growth, operating margin growth, earnings growth, earnings revisions, earnings momentum, and return on equity. For more information, get Portfolio Grader’s complete analysis of XENE stock.

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

Calithera Biosciences, Inc. (CALA) is having a tough week. The company’s rating falls from a C to a D. The company also gets F’s in return on equity and free cash flow. For more information, get Portfolio Grader’s complete analysis of CALA stock.

Raptor Pharmaceutical Corp. (RPTP) slips from a C to a D this week. Raptor Pharmaceutical Corp. researches existing drugs to improve them through specialized drug targeting methods and formulation changes. The company also gets F’s in return on equity and free cash flow. For more information, get Portfolio Grader’s complete analysis of RPTP stock.

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

Cancer Genetics, Inc.’s (CGIX) rating weakens this week, dropping to a D versus last week’s C. The company also gets F’s in return on equity and free cash flow. For more information, get Portfolio Grader’s complete analysis of CGIX stock.

This is a rough week for Eleven Biotherapeutics, Inc. (EBIO). The company’s rating falls to D from the previous week’s C. 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 EBIO stock.

Heat Biologics, Inc. (HTBX) slips from a C to a D this week. The company also gets F’s in return on equity and free cash flow. For more information, get Portfolio Grader’s complete analysis of HTBX stock.

Peregrine Pharmaceuticals, Inc. (PPHM) earns a D this week, moving down from last week’s grade of C. Peregrine Pharmaceuticals, Inc. is a clinical-stage biopharmaceutical company developing first-in-class monoclonal antibodies for the treatment of cancer and viral infections. 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 PPHM stock.

Celladon Corporation (CLDN) declines this week from a D to a F. The company also gets F’s in return on equity and free cash flow. For more information, get Portfolio Grader’s complete analysis of CLDN 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.