The unconditional approval by the German Federal Cartel Office is a positive development for AbbVie, likely to be viewed favorably by investors. It suggests that regulatory barriers are being overcome, which is a critical step in the merger process. This news could lead to a short-term positive impact on AbbVie's stock price as it moves closer to successfully acquiring ImmunoGen.

The approval from the German Federal Cartel Office is a direct endorsement of the merger between ImmunoGen and AbbVie. For ImmunoGen, this news is highly relevant and important as it brings the company closer to the completion of the merger. Investors are likely to react positively to this development, potentially leading to an increase in ImmunoGen's stock price in the short term.