Argenx SE (ARGX) shares tumbled 12.80% in pre-market trading on Thursday following the release of its first-quarter earnings report. The significant drop comes despite the company reporting better-than-expected earnings per share, highlighting investors' concerns about other aspects of the financial results.

The biopharmaceutical company reported Q1 earnings of $2.58 per diluted share, surpassing analysts' expectations of $2.41 and marking a substantial improvement from the $1.04 loss per share in the same quarter last year. Operating income for the quarter ended March 31 rose to $807.4 million, up from $412.5 million in the previous year. However, this figure fell short of the $817.6 million forecast by analysts surveyed by FactSet.

The sharp stock decline, despite beating earnings per share estimates, suggests that investors may be focusing on the missed operating income target or harboring concerns about future growth prospects. It's possible that market expectations were set higher than the analyst consensus, or that other factors not explicitly mentioned in the earnings report are influencing investor sentiment. As the trading day progresses, market watchers will be keen to see if Argenx can recover from this pre-market plunge.