Small-cap stocks strayed far behind the sliding major indices Tuesday, and one of the worst performers was Inovio Biomedical ( INO).

The San Diego-based company plummeted 36% to $2.20 after halting patient enrollment in both of its late-phase pivotal studies on an investigational therapy called selective electrochemical tumor ablation (SECTA). An independent data-monitoring committee noted, among other things, that the mortality rate among the head- and neck-cancer patients treated with SECTA was higher than among those who underwent surgery.

Shares of North American Scientific ( NASI), which likewise makes cancer-treatment products, slid 18% to $1.23 after the California-based company's second-quarter revenue fell 22.9% year over year to $6.2 million, even though per-share losses halved to 11 cents.

Women's apparel retailer Cache ( CACH) sank 12.2% after it slashed guidance for the rest of the year to fall far short of Wall Street expectations. Cache shares fell $1.98 to $14.26 and weighed on the Russell 2000 index, which recently gave up 0.8% at 848.27.

Internet-protocol-video semiconductor Sigma Designs ( SIGM), another Russell 2000 member, tumbled 8.3% after an analyst with American Technology Research maintained his sell rating on the stock. He cited the company's predicted slowdown in sequential sales growth, which he attributes to mounting customer pressure on Internet-protocol TV pricing, as well as "looming" competitive threats. Despite positive results for the most recent quarter, Sigma shares lost $2.40 to $26.68.

The S&P SmallCap 600 also slid 0.8% to 440.72 as one of its components, Arizona's Inter-Tel ( INTL), traded lower on news that Vector Capital won't, after all, make a $26.50 per-share cash offer to buy the company, as it had said it might do last month. Inter-Tel shares lost 2.8% to $25.75.

On the flip side, Graham ( GHM), which makes vacuum and heat-transfer equipment, soared 27.6% to $23.19 after per-share earnings more than tripled from last year to 86 cents a share on 30.8% higher revenue. Sutron ( STRN), maker of products for the monitoring of meteorological and other data, leapt 22.2% to $9.90 after reporting "record" customer orders and contracts in May totaling some $9.3 million.

Virginia-based Sierra Wireless ( SWIR) ratcheted up after a CIBC World Markets analyst predicted that the Canada-based communications-equipment maker is poised to benefit from increased proliferation of third-generation cell-phone technology. The analyst upped Sierra to sector outperform from sector perform, upon which shares jumped 11.7%, or $2.58, to $24.55.

And Oncolytics Biotech ( ONCY), also based in Canada, said an early-phase study preliminarily showed that its Reolysin cancer treatment induced antitumor activity and can be systemically administered in patients with advanced and metastatic cancers. Shares leapt 8.7% to $2.26.

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