For decades, a small group of plaintiffs lawyers have been pressing claims against companies that made and sold a synthetic estrogen known as diethylstilbestrol, or DES, which was prescribed to millions of pregnant women to ward off premature births and miscarriages from 1948 to 1971. But after it was linked to a rare vaginal cancer in women whose mothers used it, DES was taken off the market. Studies have since shown that DES didn’t prevent miscarriages, and exposure to the drug in utero has been associated with numerous other illnesses including infertility and breast cancer.

Cases against drug manufacturers have settled in dribs and drabs over the past three decades, and claims against the companies have never been litigated in a large-scale class action. On January 9, plaintiffs lawyers missed a chance to strike a body blow to defendants facing breast cancer-related claims over DES, when the first such case to go before a jury settled in the midst of trial. The confidential deal with defendant Eli Lilly & Co. was reached on the second day of testimony before U.S. Magistrate Judge Marianne Bowler in Boston.