An investment company that lists former Boston Celtic player and coach M.L. Carr as a partner has been hit with a $1.5 million lawsuit.

A holding company KDRL Holdings, LLC, filed suit against NTV Management, Inc., in Delaware, claiming that NTV — which stands for New Technology Ventures and counts Carr as a partner — failed to pay off a debt even after amending the terms multiple times.

“As a result of NTV’s serial failure to satisfy the terms of the note, the parties amended that original note three times. All the terms of the original note and its amendments were proposed by NTV. The final maturity date for payment of all the cash owed to KDRL was September 30, 2024. As NTV admits, the repayment of the principal and 50% interest in cash has been due and owing,” the lawsuit states.

The lawsuit was filed in the Superior Court of the State of Delaware as both KDRL and NTV are incorporated in the state, though both businesses have operations in Massachusetts, according to the complaint. NTV lists a Massachusetts business address in Newton Lower Falls, according to its website.

KDRL’s complaint states that “NTV has no justification for its failure to pay” and that Carr himself continually assured KDRL’s directors that he personally “guaranteed” that the debt would be paid off by the end of 2024.

“He repeated that statement a few times and was quite emotional, including by emphasizing how important he was and that he was a man of his word and always honored his commitments,” the lawsuit states.

The loan began when Hal Chapel, the managing director of NTV, approached KDRL managers David Rosenberg and Louis Karger in March 2022, according to the suit. Chapel was seeking $3 million in debt financing for QuantumXchange, a cybersecurity firm NTV holds shares in.

KDRL agreed to loan $1 million to NTV and agreed to terms drafted by NTV, according to the suit. The interest would be paid in 50% cash and 50% shares of QuantumXchange, Inc., which is also incorporated in Delaware. It was originally all due to be repaid at the end of September 2023.

Carr played with the Boston Celtics from 1979 to 1985, during which the team won two NBA World Championships: in 1981 and 1984, according to his NTV biography. He rejoined the team as the director of basketball operations in 1994, a year in which he was also head coach, through the 1997 season when he became the director of corporate development for the team.

The Herald has requested comment from representatives of KDRL, NTV and QuantumXchange, as well as a management company representing Carr.