Vertex Pharmaceuticals has increased by 10% its stake in the partnership with CRISPR Therapeutics to develop and commercialize the gene therapy drug CTX001. Vertex will now be responsible for 60% of the costs and receive 60% of the profits from future sales of CTX001 worldwide. The company will pay CRISPR an upfront payment of $900 million and $200 million after the first regulatory approval of CTX001.