TCA9509: TCA9509 / Connection of unused bus

Part Number: TCA9509

Hi,

I understand that TCA9509 has SDA and SCL bus for I2C bus, but now my customer consider to use it other purpose and they need only one channel. Then can they leave open the unused bus or need to tie VCCx or GND?

Best Regards,

Satoshi / Japan Disty