Credit Suisse was on course to shed a quarter of its value on Wednesday after its largest shareholder said it could not provide any more support, pushing the Swiss bank's CEO to make new assurances on its financial strength. Saudi National Bank (SNB), which holds 9.88% of Credit Suisse, said it would not buy more shares in the Swiss bank on regulatory grounds. The Swiss bank's shares were down about 24% early afternoon on Wednesday, after hitting a new record low.