UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Jan. 31, 2012	Jan. 31, 2011
Operating activities:
Net loss	$ (6,111)	$ (1,060)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	2,612	1,578
Depreciation expense	65	30
Change in fair value of warrant liability	(354)	0
Changes in operating assets and liabilities:
Accounts receivable	88	(319)
Grant receivable	12	(367)
Prepaid expenses, deposits and other	166	120
Restricted cash	(150)	0
Accounts payable	43	1,139
Accrued liabilities	42	(67)
Deferred revenue	(117)	(550)
Net cash (used in) provided by operating activities	(3,704)	504
Investing activities:
Purchase of property and equipment	(371)	(47)
Net cash (used in) investing activities	(371)	(47)
Financing activities:
Purchase of treasury stock	0	(73)
Proceeds from exercise of options and warrants	98	2
Net cash provided by (used in) financing activities	98	(71)
Exchange rate effect on cash and cash equivalents	2	(17)
Net change in cash and cash equivalents	(3,975)	369
Cash and cash equivalents, beginning of period	10,457	2,572
Cash and cash equivalents, end of period	$ 6,482	$ 2,941