(Reuters) - Insurance Commissioner Dave Jones on Tuesday filed a complaint on behalf of the State of California against AbbVie Inc, alleging the drugmaker gave illegal kickbacks to healthcare providers to prescribe its blockbuster drug, Humira.

AbbVie shares fell 2.5 percent to $92.98 on Tuesday afternoon.

The regulator alleged that AbbVie engaged in a far-reaching scheme including cash, meals, drinks, gifts, trips and patient referrals, as well as free and valuable professional goods and services to physicians to induce and reward Humira prescriptions.

“We believe the allegations are without merit. AbbVie operates in compliance with the many state and federal laws that govern interactions with healthcare providers and patients,” the company said in a statement.

AbbVie said it provides a number of support services for patients, once they are prescribed Humira, that both educate and assist patients with their therapy, including nursing support.

“They in no way replace or interfere with interactions between patients and their healthcare providers,” AbbVie said.

The case, filed in Alameda County Superior Court, alleged that private insurers have paid out $1.2 billion in Humira-related pharmacy claims.

The allegations of AbbVie’s misconduct were brought to the attention of the department by a whistleblower, a registered nurse who was employed as an AbbVie Nurse Ambassador in Florida.

Humira is the world’s best-selling prescription medicine and has long buoyed AbbVie’s business, accounting for some two-thirds of overall sales.

“AbbVie spent millions convincing patients and health care professionals that AbbVie Ambassadors were patient advocates—in fact, the Ambassadors were Humira advocates hired to do one thing, keep patients on a dangerous drug at any cost,” Insurance Commissioner Dave Jones said.