Grail said today that it has raised more than $900 million in a Series B round led by Arch Venture Partners. Johnson & Johnson Innovation made the largest investment of any involved in the massive financing, Grail said in a statement, but it was also helped by three other drugmakers (Bristol-Myers Squibb, Celgene, Merck), tech giant Amazon, the venture arm of healthcare services firm McKesson, China-based Tencent Holdings, and Varian Medical Systems, a developer of radiation cancer treatments.