From Religious People of Interest in the Shoah:
Pius XI in the late 30s made a monumental move: the first writing of an Encyclical which at least in part denounced racial anti-Semitism.
It is referred to as "the hidden Encyclical".
Pius XI requested American Jesuit Msgr LaFarge to draft the statement which upheld traditional Catholic doctrine against Jewish doctrine but decried racism against the Jews, and countered at least part of the intent of the 1933 Vatican Concordat with Nazi Germany. Ledochowski was the austere politician and Jesuit General at the time, and he was not in favor of the new document. It mysteriously disappeared and Pius died before the signing, although it was one of the last documents on his desk.
The document: Humani Generis Unitas, or "The Unity of the Human Race" might have made a difference in the Vatican's allowance of the Third Reich's policies. Pius died, Pius XII, more a politician and diplomat than theologian and with ties to Germany and von Papen took office rapidly.
Ledochowski is credited with being instrumental in the suppression of the document.