The European Commission (EC) Tuesday announced its decision to prohibit US biotechnology company Illumina’s acquisition of the cancer-test provider GRAIL, citing concerns on the takeover’s impact on competition in the market. The Commission opened an in-depth investigation into the proposed acquisition last July, citing concerns that Illumina could engage in vertical input foreclosure strategies considering its leading position in the market.

The EC, the EU’s antitrust watchdog, said in a statement, “[The] merger would have stifled innovation, and reduced choice in the emerging market for blood-based early cancer detection tests,” before adding that Illumina did not propose sufficient remedies to alleviate these concerns.

The concerns arose from the merger, which led to a vertical integration of Illumina—a market leader in next generation sequencing (NGS) systems for genetic and genomic analysis—with GRAIL, a customer of Illumina using its technology to develop blood-based early cancer detection tests.

In the statement, the EC justified its decision:

The acquisition would have enabled and incentivised Illumina to foreclose GRAIL’s rivals, who are dependent on Illumina’s technology, from access to an essential input they need to develop and market their own tests. As a result, GRAIL’s competitors would be put in a disadvantaged position compared to GRAIL.

The EU Commissioner for Competition Margrethe Vestager emphasized the EC’s concerns, stating that “Illumina is currently the only credible supplier of a technology allowing to develop and process these tests.” Vestager voiced concern that the transaction would have incentivized Illumina to cut off market competitors from GRAIL’s technology.

General Counsel of Illumina Charles Dadswell said Illumina was disappointed in the EC’s decision. Dadswell added, “Illumina can make GRAIL’s life-saving multi-cancer early detection test more available, more affordable, and more accessible – saving lives and lowering healthcare costs.”

Illumina is currently reviewing the EC order and intends to appeal the decision.