Although biotech has been a strong area of the market for quite some time, the past year has been a brutal stretch for this segment. In fact, the top biotechnology ETF (IBB - ETF report) has seen a loss of roughly 25.5% in the past 52 weeks, making for a massive underperformance when compared to the broad markets in the same time frame.

And while there has been a bit of a comeback lately, the last few trading days have certainly put an end to that, as IBB has lost nearly five percent in the past five trading sessions.

But which stocks in particular have been driving this horrendous return as of late for this popular ETF? The following stocks are definitely the culprits as they have all lost more than the overall ETF with several slumping more than 10% in the time frame. Let’s take a quick look at a few of the biggest contributors to IBB’s underperformance as of late below:

Biogen (BIIB - Analyst Report)

Biogen shares have been in trouble lately thanks to a weak report on its MS drug results. The Phase 2 trial failed to meet both its primary and secondary endpoints and shares of BIIB plunged as a result.

The stock remains a Zacks Rank #3 (Hold), while it has a VGM Score of ‘A’, so fundamentals are still looking promising for this stock despite the recent drop.

Alexion Pharma (ALXN - Analyst Report)

More poor drug trial news to report back on, as ALXN suffered from a Phrase III letdown in its Soliris drug, as this missed its primary efficacy endpoint. Shares sold off significantly as a result of this release, and it is especially disappointing since it comes in Phase III.

The stock is currently a Zacks Rank #4 (sell) while it has Value and Growth Style Scores of ‘D’ so there are definitely better prospects out there in the biotechnology world right now.

BioMarin Pharma (BMRN - Analyst Report)

And BioMarin struggled as its main competitor in the Muscular Dystrophy market, Sarepta (SRPT - Analyst Report) , saw some somewhat promising news from the FDA. This hope for SRPT along with BioMarin’s woes in the space, lead many investors to continue their exodus out of BMRN shares which was to IBB investors’ detriment yet again.

This stock is also a Zacks Rank #3 (hold), but the quarterly Earnings ESP is plunging, coming in at -13.5%. This suggests that the most recent estimates have been pretty weak for BMRN and that a downgrade may be on the horizon if this trend continues.

Regeneron (REGN - Analyst Report)

This was a bit of a surprise addition to the list of biggest losers on the week, as REGN actually reported positive results from a Phase III trial. However, the perception of the broader space has swung negative and REGN was unable to escape the downturn, falling more than 7% on the week.

Arguably shares had run up a bit too high in the preceding month and this was just a bit of a snap back to reality. Still, this remains a decent choice in the space thanks to solid EPS growth projections and a Zacks Rank #3 (Hold). And unlike others on the list, it has been seeing some relatively positive news lately.

Bottom Line

The four components listed above make up roughly one-fifth of the total exposure in IBB so they are bound to have a big impact on its overall performance. Investors in IBB will definitely need to see a turnaround here before the fund can make a comeback, and return to its storied past.

However, you could easily argue that the boom is starting to fade in the biotech sector, and especially so given the coming political headwinds for the space. Given that, it may be time to look to other health care ETFs for now, at least until the firestorm dies down in this often-volatile corner of the stock market.