BOSTON (

TheStreet

) -- Checking in on the "Biotech Bubble: Yeah or Nay?" debate:

Before we start, let's agree the biotech sector is still having an unbelievable year.

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IBB

data by

YCharts

But biotech stocks have underperformed the broader market in the past month.

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IBB

data by

YCharts

Momentum-driven biotech stocks -- mostly small- and mid-cap -- have been hit with some serious selling over the past month. These were some of the sector's highest flyers, but not lately. I'm talking about stocks like:

Celldex Therapeutics

(CLDX) - Get Report

:

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CLDX

data by

YCharts

Clovis Oncology

(CLVS) - Get Report

:

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^NBI

data by

YCharts

and

Immunomedics

(IMMU) - Get Report

:

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IMMU

data by

YCharts

2013 is shaping up to be a record year for biotech IPOs, but not all of the stellar debuts have staying power.

Bluebird Bio

(BLUE) - Get Report

:

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BLUE

data by

YCharts

Alcobra Pharma

(ADHD)

:

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ADHD

data by

YCharts

Onconova Therapeutics

(ONTX) - Get Report

:

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ONTX

data by

YCharts

Stemline Therapeutics

(STML) - Get Report

:

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STML

data by

YCharts

Some biotech IPOs keep moving higher, like...

Receptos

(RCPT)

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RCPT

data by

YCharts

and

Ambit BioSciences

(AMBI)

:

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AMBI

data by

YCharts

Big-cap biotech stocks are still performing strongly. Is there an investor flight to quality companies like

Gilead Sciences

(GILD) - Get Report

,

Amgen

(AMGN) - Get Report

,

Biogen Idec

(BIIB) - Get Report

and

Celgene

(CELG) - Get Report

?

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GILD

data by

YCharts

It's definitely NOT been a hard-knock life for orphan drug stocks in 2013:

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AEGR

data by

YCharts

But investors have sent orphans begging in the past month:

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AEGR

data by

YCharts

-- Reported by Adam Feuerstein in Boston.

Follow @AdamFeuerstein

Adam Feuerstein writes regularly for TheStreet. In keeping with company editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback;

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