The grim accusation rocked a major New York City hospital late last year: An emerging gastroenterologist had been charged with first-degree rape. Prosecutors said he had drugged a girlfriend and filmed the assault at his apartment.

The doctor, Zhi Alan Cheng, 33, was fired from the medical center, NewYork-Presbyterian Queens, in December after his arrest.

Then, when investigators searched his electronic devices, they uncovered a disturbing stash: dozens of short videos showing Mr. Cheng sexually abusing other women at his home in Astoria and at the hospital where he worked, prosecutors said.

On Monday, Mr. Cheng was charged with 50 new counts, including rape, sexual abuse, assault, misdemeanor drug possession and unlawful surveillance, in criminal court in Queens. He pleaded not guilty at his arraignment.

The new charges are based on the former physician’s encounters with six women, including patients and dating partners.

Prosecutors said the assaults were part of a brutal, methodical pattern in which Mr. Cheng drugged women with liquid anesthesia before attacking them. Many later woke with no memory of what had happened.

Investigators said there were additional victims whom they had yet to identify, including one woman whose sexual assault Mr. Cheng recorded at the hospital.

At least five other unidentified women were assaulted at hotel rooms or at homes in New York, Las Vegas, San Francisco and Thailand over the past several years, according to the videos’ data, the prosecutors said.

In a statement, Melinda Katz, the Queens district attorney, urged anyone with potential leads about other victims to come forward. Ms. Katz said the evidence revealed “a sexual predator of the absolute worst kind, a serial rapist” who was willing to violate “every standard of human decency.”

Mr. Cheng made his plea through his lawyer, Jeffrey Einhorn, who declined to say more. “It’s too early,” he said outside the court.

Mr. Cheng was returned to a jail on Rikers Island, where he has been held since the initial charges.

The new charges follow several recent cases in New York of powerful medical professionals exploiting their access to patients to sexually abuse them.

They include Robert A. Hadden, a former gynecologist at prominent hospitals who was sentenced last month to 20 years in prison for sexually assaulting patients, and Ricardo Cruciani, who was convicted of similar sex crimes last year.

Unlike those doctors, Mr. Cheng — who attended Albany Medical College in the 2010s before completing his residency at California Pacific Medical Center in San Francisco — had only recently received his New York medical license, in June 2020, online records show.

The assault of his first known victim at NewYork-Presbyterian Queens, in Flushing, came less than a year later, according to court documents.

Angela Karafazli, a spokeswoman for the hospital system, said in a statement that “we are appalled and deeply saddened by what these victims and their families have endured.”

The victims who have been identified ranged from 19 to 47 years old, the authorities said, and Mr. Cheng often took multiple recordings of each assault.

Mr. Cheng was arrested in December 2022 after the authorities said his girlfriend at the time discovered videos of him assaulting her. The police later found drugs — including fentanyl, ketamine, LSD and several anesthetics typically used in surgeries — and devices with dozens of other recordings at his home.

In one case, Mr. Cheng is accused of filming himself groping a 37-year-old patient as she lay unconscious at the Queens hospital in 2021.

A short time later, prosecutors said, he raped a woman whom he met on a dating app. In videos of her assault, a small brown bottle was visible on his bed, according to the authorities, who said they had recovered a similar bottle from his apartment that contained a powerful anesthetic.

And in a third episode that summer, a 19-year-old woman had sought treatment at the hospital for severe pain from gallstones. Mr. Cheng performed an unnecessary rectal exam, and later injected the woman’s IV line with an “unknown substance” and sexually assaulted her, her lawyers and prosecutors said.

The woman filed a lawsuit against the hospital in June under a pseudonym, accusing the center of conspiring “to cover up her assault” and failing to intervene after she told staff Mr. Cheng had administered a painful injection that made her lose consciousness.

The NewYork-Presbyterian system fell under scrutiny recently related to Mr. Hadden’s case, agreeing, along with another hospital, to $236 million in settlements with more than 220 patients. It also employed a former urologist, Darius Paduch, who was charged in April with sexually abusing a Manhattan patient when the patient was a minor.

Ms. Karafazli said the system had been reviewing its “numerous stringent patient safety policies and protocols” for potential areas of improvement. She added that the hospital had provided “additional training for all employees” after Mr. Cheng was arrested.

Adam Slater, a lawyer who filed the 19-year-old’s suit with another firm, Liakas Law, said the hospitals had shown a repeated “failure to protect patients.”

“It’s not an isolated incident,” Mr. Slater said. “It’s systemic.”