Corning's stock plummeted 5.12% during intraday trading on Monday, extending recent losses as investors grapple with elevated valuation metrics and broad weakness across the optical communications sector.

The decline reflects multiple headwinds, including Corning's price-to-earnings ratio remaining near 100x and the optical communications sector valuation sitting at the 99th percentile of its five-year range. This leaves minimal margin of safety and has triggered profit-taking following a brief technical rebound earlier in the week. Additionally, prior executive share sales and market concerns over the sustainability of optical communications capital expenditure continue to weigh on sentiment.

Broad sector pressure contributed to the selloff, with peers including Coherent, Lumentum, and Credo also declining significantly in pre-market and regular trading sessions. Despite Citigroup raising its price target on Corning to $240 from $225 and maintaining a Buy rating, the market appears to be awaiting earnings verification ahead of Corning's Q2 report scheduled for later this month.