Today was an up day for the S&P/ASX 200 (INDEXASX: ^AXJO) (ASX: XJO), with the index rising 1% to 5139 points, making up most of the ground lost since the start of the year.

These four shares significantly underperformed however, and here’s why:

Clinuvel Pharmaceuticals Limited (ASX: CUV) fell 8% to $3.30 on no news, reversing most of the gains made in the aftermath of the company’s interim results release on 19 February. Investors were seemingly pleased with the company’s progress towards commercialising its chief SCENESSE treatment in the US, although as yet Clinuvel remains unprofitable. Today’s fall returns Clinuvel to its average price over much of the past year, with shares up 5% in the past 12 months.

Ensogo Ltd (ASX: E88) plunged 11% to $1.38 on no news today as investor bearishness grows in the aftermath of the company’s interim results, which saw an 8.5% decline in revenue and an 18.4% improvement in the company’s net loss after tax. The loss was characterised by significant goodwill impairments to legacy assets, and management claims there are more than 10 times as many products available for sale on its platform than there were 12 months ago.

Ensogo shares are down 49% in the past year.

Amaysim Australia Ltd (ASX: AYS) lost 4% to $1.82 as selling pressure continues in the wake of a disappointing half-yearly report that was characterised by an increase in trading volume and selling activity in the days before its release date. Investors were possibly spooked by the slim profit figure, as well as management acknowledgement that its revenues remained under pressure from high competition. Amaysim remains well funded with $16 million cash at bank, and is now trading approximately in line with its launch price, which could give interested investors a second bite at the apple.

Amaysim has only been listed for eight months, and shares are trading flat since then.

Vocus Communications Limited (ASX: VOC) fell 4% to $7.90 in continuing volatility today as the market appears unsure just how to price the company. Vocus shares recently traded as low as $7 in the lead-up to the half-yearly report, which apparently reminded investors of the potential contained in the company’s recent acquisitions. Vocus is now one of the largest telecommunications players in Australia, after TPG Telecom Ltd (ASX: TPM), and Telstra Corporation Ltd (ASX: TLS). With synergies still to be unlocked from its acquisitions combined with rapidly growing consumer demand for data, Vocus appears to have a strong pipeline for growth ahead of it.

Vocus shares are up 42% in the past year.

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Motley Fool contributor Sean O'Neill has no position in any stocks mentioned. Unless otherwise noted, the author does not have a position in any stocks mentioned by the author in the comments below. The Motley Fool Australia has no position in any of the stocks mentioned. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy. This article contains general investment advice only (under AFSL 400691). Authorised by Bruce Jackson.