Fifteen states that led the effort to block a controversial bankruptcy plan for OxyContin-maker Purdue Pharma have abandoned the fight.

That’s according to court documents reviewed by NPR and filed by a mediator late Wednesday as part of a federal bankruptcy proceeding in White Plains, N.Y.

Among the states that have agreed to sign on to the bankruptcy deal are Massachusetts and New York, whose attorneys general had mounted fierce legal opposition to the agreement.

The other states now abandoning their opposition to the deal are: Colorado, Hawaii, Idaho, Illinois, Iowa, Maine, Minnesota, Nevada, New Jersey, North Carolina, Pennsylvania, Virginia and Wisconsin.

According to the mediator, nine states have yet to agree to the Purdue Pharma bankruptcy plan. They include Connecticut, where the company is headquartered, as well as California, Delaware, Maryland, New Hampshire, Oregon, Rhode Island, Vermont and Washington. The District of Columbia also hasn’t agreed to the deal.

“The negotiations were difficult and hard-fought, with the outcome uncertain,” said federal bankruptcy Judge Shelley C. Chapman in the legal filing.

The settlement plan, which is now all but certain to be finalized next month, would shelter members of the Sackler family, who own Purdue Pharma, and many of their associates from future opioid lawsuits.

In return, the Sacklers have agreed to give up ownership of the bankrupt drug company. They will also pay out roughly $4.2 billion from their private fortunes in installments spread over the next decade.

According to the mediator’s report, the Sacklers have now agreed to boost their settlement payment by a relatively modest amount – roughly $50 million.

The deal also includes a “material expansion” of the public document repository already created under the settlement plan that aims to provide some transparency about Purdue Pharma’s role in the opioid epidemic.

Purdue Pharma has pleaded guilty twice to federal criminal charges related to its opioid marketing practices, first in 2007 and again last year.

The Sacklers have never faced charges. Under this deal, they will admit no wrongdoing and will remain one of the wealthiest families in the U.S.