Argenx SE (ARGX) shares plummeted 13.54% 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. However, operating income for the quarter ended March 31 rose to $807.4 million, up from $412.5 million in the previous year, falling short of the $817.6 million forecast by analysts surveyed by FactSet.

Adding to investor uncertainty, Argenx maintained its financial guidance for the fiscal year 2025, targeting combined selling, general and administrative (SG&A) and research and development (R&D) expenses of approximately $2.5 billion. The unchanged guidance, coupled with the lower-than-expected operating income, appears to have overshadowed the positive EPS surprise, leading to the sharp pre-market decline in Argenx's stock price. As the trading day progresses, market watchers will be keen to see if Argenx can recover from this pre-market plunge and address concerns about its future growth prospects.