Roche fired back quickly, sending its own letter to shareholders urging them to support its board nominees. "We believe that our offer is full and fair and provides value certainty and liquidity to shareholders amid increasing headwinds for Illumina and the broader sequencing sector," wrote Severin Schwan, CEO of Roche Group. He warned that Illumina's growth prospects had diminished in the past year and were likely to continue to be impacted "as the gene sequencing market continues to mature and prices decline." Schwan said going forward, Illumina would have to invest heavily to expand its market share in an increasingly competitive global market. Roche first made its intentions clear on January 26. Illumina's board immediately adopted a "poison pill" strategy that would take effect should any one entity acquire 15 percent of the company's shares.