In what looks like a sequel to March 2014, high-flying biotechnology stocks and exchange traded funds are retreating amid talk of frothy valuations and a biotech bubble.

At least temporarily, Friday March 20 marked the top for several of the largest biotech ETFs. That is when big-name ETFs, such as the iShares Nasdaq Biotechnology ETF (NasdaqGS: IBB), the largest biotech ETF, and the Market Vectors Biotech ETF (NYSEArca: BBH) touched all-time highs after shares of Biogen (NasdaqGS: BIIB) climbed after the company said an early-stage study revealed its Alzheimer’s drug, aducanumab, stemmed cognitive decline in patients compared with those taking a placebo. [Biogen Boosts Biotech ETFs]

Since then, IBB is off more than 6% while BBH is down nearly as much. The First Trust NYSE Arca Biotechnology Index Fund (NYSEArca: FBT), which has risen to acclaim for not only its performance (FBT is the best-performing non-leveraged ETF of any type since March 2009), but also for its asset-gathering proficiency (the ETF is now the second-largest biotech fund) is off 6.4% since March 20. TheSPDR S&P Biotech ETF (NYSEArca: XBI) has been especially hard hit with a loss of nearly 8%.

Some prescient and risk-tolerant traders were prepared for the biotech ETF treat. From March 19 through March 24, investors pulled $268 million from IBB and $128.5 million from XBI. While it is not a massive amount, nearly $18 million has flowed into the ProShares Ultrashort Nasdaq Biotechnology (NasdaqGM: BIS) over the past week.

BIS is the double-leveraged inverse answer to IBB and, at least in the short-term, the former is doing an admirable job of delivering twice the daily inverse returns of the latter. Over the past week, BIS is up nearly 13%, better than double IBB’s 6.2% loss over the same period.

BIS has hauled in nearly $56 million in assets this year, bring its assets under management tally close to $110 million. Like any leveraged ETF, BIS has its risks and those risks were on full display last year. BIS surged as biotech stocks faltered last March and April, but the biotech rebound was so voracious that BIS was forced into a 1-for-5 reverse split last November. [Reverse Splits Coming for some ProShares ETFs]