Exhibit 99.1 GCT Semiconductor Holding, Inc. Provides Business Update and Reports Fourth Quarter and Full Year 2025 Financial Results Commercial Shipments of 5G Chipsets Exceeded 1,900 Units in Q4, Reflecting Continued Progress Toward Volume Production Ramp Company Expects Sequential Quarterly Growth in Revenue and 5G Chipset Shipments Throughout 2026 SAN JOSE, CA – March 25, 2026 – GCT Semiconductor Holding, Inc. ("GCT" or the "Company") (NYSE: GCTS), a leading designer and supplier of advanced 5G and 4G s ...