Health stocks followed the broader markets higher at the start of the week amid various earnings.

The Nasdaq and Amex biotech indices and the Amex Pharmaceutical index stretched into the green -- but by less than a percentage point -- on Monday.

Helping the indices along, biotechs Amgen ( AMGN - Get Report) and Biogen Idec ( BIIB - Get Report), were up 2.1% and 1.6%, respectively. While pharmas Wyeth Abbott ( ABT) and Merck ( MRK) added 2.2%, 1.9% and 1.6%.

Also rising, Isis Pharmaceuticals ( ISIS) reported a first-quarter loss of $4.3 million, or 5 cents a share, in the recent quarter, narrowed from a loss of 16 cents a share a year prior. Revenue grew to $21.4 million, from $2.5 million, while Wall Street analysts were looking for a loss of 10 cents a share on revenue of $22.1 million. Isis shares rose 7.4% to $12.64.

Of those stocks losing ground, Xoma ( XOMA - Get Report) posted a first-quarter loss of $14.2 million, or 11 cents a share, vs. a loss of $15.9 million, or 14 cents a share, a year prior.

Revenue edged down to $12.1 million from the $12.3 million in the 2007 period and falling short of its the Thomson Reuters consensus. Analysts were expectign a loss of 11 cents a share on revenue of $16.4 million. Revenue reflects royalties from Genentech's Lucentis and Raptiva and also Xoma's contacts with Schering-Plough , Takeda and the National Institute of Allergy and Infectious Diseases (NIAID).

Xoma shares were down 7.3% at $2.15.

Shares of biopharmaceutical company GTx Inc. ( GTXI) fell 3.2% to $16.91 after the company aired its quarterly results. GTx said its loss widened to $12.7 million, or 35 cents a share, from $8.1 million, or 23 cents a share, in the year-earlier period.

Revenue rose to $4.5 million from $1.7 million -- analysts surveyed by Thomson Reuters had expected a loss of 30 cents a share on revenue of $3.7 million.

Looking ahead, GTx said that it anticipates a full-year 2008 loss of between $52 million and $62 million, while the Thomson Rueters consensus calls for a loss of $44.7 million.

In other earnings, Medarex said that factoring out certain items such as the sale of 2.5 million shares of Genmab stock and a 4-cent per-share stock-based compensation expense, it lost 30 cents a share in the recent quarter. Revenue edged up to $12 million from $11.5 million the prior-year period.

Analysts polled by Thomson Reuters had pegged a loss of 38 cents a share on sales of $11.6 million. (Consensus estimates typically factor out one time items but include stock-based compensation expenses.)

Shares edged down 1.1% to $7.03 on lighter-than-average volume.

Away from earnings, Morgan Stanley analyst Steven Harr downgraded ImClone ( IMCL) to underweight from equal weight on Monday, ahead of data set to be released at the American Society of Clinical Oncology meeting in June. Harr said in a note to investors that he believes the data for Erbitux in both lung an colorectal cancers won't meet expectations. ImClone shares were off 7.3% at $41.58.