Updated from 12:09 p.m. EDTBiogen Idec ( BIIB) is expected to turn in solid first-quarter earnings Thursday, with investors likely to be focused more on performance of the multiple sclerosis drug Tysabri and management comments about merger-and-acquisitions activity than on the company's bottom-line result. The Cambridge, Mass.-based biotech firm is expected to grow first-quarter earnings by 22% to $1.01 a share on total revenue of $1.08 billion, according to Thomson Reuters. New patient growth for Tysabri in the first quarter is likely to be the most important data point from Thursday's earnings announcement, with analysts generally expecting little change from the 6% growth rate of new patient additions during the fourth quarter of last year. On a revenue basis, analysts are looking for worldwide sales of Tysabri of $239 million, a 10% sequential increase. This follows disappointing fourth-quarter sales that were down sequentially and well below analyst estimates. Biogen shares Tysabri revenue with Irish drug maker Elan ( ELN). Tysabri's performance has been hurt by five cases of patients being diagnosed with progressive multifocal leukoencephalopathy, or PML, a serious brain infection. Last month, Biogen executives laid out plans to re-accelerate Tysabri patient growth, including new research into treatments that could potentially reverse the effects of PML. The company has also pointed to internal market research showing that a large percentage of neurologists expect to increase use of Tysabri over the next six months while only a small percentage of doctors plan to prescribe less Tysabri. Biogen CEO Jim Mullen will probably field questions during Thursday's conference call regarding whether the company is a takeover target. This follows market rumors that a large pharmaceutical company might be eyeing Biogen as an acquisition target. The chatter helped drive Biogen shares higher last week.