Gandhi's items were auctioned off by the Antiquorum Auctioneers for $1.8 million. Otis said he will file a case in the New York State Supreme Court in an effort get the items back.
He also said his lawyers are finalising the details. He did not reveal the grounds on which he would seek the items back.
The auction included Gandhi's iconic round eye glasses and other personal belongings, including a pocket watch, a pair of sandals, glasses, bowl and a plate.
Earlier Otis also said that he had Gandhi's blood report and a signed telegram in his possession.