Is Zakat obligatory on business profits whose debts have not yet been settled?

Profits are not subject to Zakat. Debt waives Zakat on intrinsic assets (gold, silver, currency, trade goods), unless there is surplus wealth beyond basic needs from assets not subject to Zakat. In that case, it should be used to settle the debt. Profits are subject to Zakat if a hawl (full lunar year) has passed on them and they reach the nisab (minimum taxable amount).