SAN FRANCISCO — The plaintiffs lawyers that once secured the largest-ever award in a gender discrimination suit from a Cravath, Swaine & Moore client have a new target: Japanese pharmaceutical firm Daiichi Sankyo.

In a complaint filed Monday in the Northern District of California, six women represented by the employment law boutique Sanford Heisler accuse Daiichi Sankyo Co. of underpaying female sales reps, failing to promote them along with male colleagues, and discriminating against pregnant employees and working mothers.

The firm’s sales strategy, the complaint alleges, relies on using attractive women to promote drugs, and male executives treat female employees as "props."

Instead of rewarding women for their success, male managers promoted less-qualified men and punished women who availed themselves of maternity leave or flexible work arrangements.

Daiichi Sankyo’s actions are a "primer on how a company should not operate or treat female employees," states the complaint in Wellens v. Daiichi Sankyo, 13-581. Janette Wipper, managing partner of Sanford Heisler’s San Francisco office, said the pharmaceutical industry has a pattern of gender discrimination in its sales ranks.

"Women don’t receive the same compensation, and they don’t receive the same promotional opportunities," Wipper said. "If they become pregnant, all of these issues are really exacerbated."

Wipper worked on a similar case against Novartis Pharmaceuticals Corp., which resulted in a record jury verdict of $250 million in 2010 and ultimately settled for roughly $175 million. To settle the case, Novartis, represented by Cravath, agreed to pay more than $100 million to class members and to implement new policies for training, evaluating and promoting employees.

A spokeswoman for Daiichi Sankyo, which has U.S. headquarters in New Jersey, said in an email that the drugmaker complies with all laws regarding equal opportunity and nondiscrimination.

The company employs approximately 3,000 people in the United States and sells drugs to treat cardiovascular disease, diabetes and melanoma.

Name plaintiff Sara Wellens, a current employee in Northern California, contends in the suit that she joined Daiichi Sankyo with three years of experience and earned a ranking of nine out of 500 sales reps at her level.

However, while men were fast-tracked for promotion and received perks and mentoring, Wellens claims she was held back because she became pregnant and took maternity leave.

After she returned, a male supervisor referred to Wellens as a "baby-maker," and an HR employee instructed her that breast-feeding could not interfere with work-related events, the suit alleges.

Other female plaintiffs said they were demoted, fired or forced to resign due to discrimination.

"All of the plaintiffs are very strong performers and really gave a lot to the company," Wipper said. "That wasn’t recognized through pay or promotional opportunities."