Spark lays out a $108M IPO and tests the biotech boom's longevity

After an unprecedented surge of biotech IPOs in 2014, the industry's eyes have turned to gene therapy upstart Spark Therapeutics, poised to pull off the biggest IPO of the new year.

Spark, planning to trade on the Nasdaq under "ONCE," expects to price 5.5 million shares at between $15 and $17 each, laying out an additional 825,000 shares for its underwriters to cover overallotments. If everything goes as well as possible, the biotech will gross $107.5 million in the process, bankrolling its work on a portfolio of one-time treatments for rare diseases.

The company has earmarked most of its potential proceeds for SPK-RPE65, an FDA-designated "breakthrough" therapy now in Phase III development to treat a group of vision-destroying ailments called inherited retinal dystrophies. Spark's pipeline also includes SPK-CHM, a treatment for the retinal disease choroideremia; and SPK-FIX, a Pfizer ($PFE)-partnered hemophilia B therapy.

Spark, a 2014 Fierce 15 honoree, has raised more than $100 million in venture cash and collaboration revenue within about a year. And, with IPO proceeds estimated at about $78.8 million, the biotech believes it's poised to play a lead role in gene therapy's recent renaissance.

But beyond its short-term importance, Spark's IPO will likely be viewed as a bellwether for how well the industry's 2014 momentum will translate into the new year.

Biotech debutantes raised a record $6.3 billion in IPO cash last year, a figure buoyed by increasing high valuations and investor fervor over technologies like cancer immunotherapies and gene therapy. Most at last week's annual JP Morgan Healthcare Conference were optimistic the good vibes would keep rolling into 2015, but for how long and to what extent remain topics of debate. And thus Spark's potential IPO, the largest and highest-profile among the latest crop, will be closely watched.

Spark's splash into gene therapy comes amid something of a second honeymoon for a field that has been through the wash cycle of biotech hype. Serious safety issues and deliverability woes long hampered gene therapy R&D, but, after years of work, a new generation of academics and investigators believes it has hammered out the right viral vectors to safely and predictably get corrective genes to their target tissues, spurring renewed hope for widespread clinical success. And that's drawn the attention of heavyweights including Pfizer, Biogen Idec ($BIIB), Celgene ($CELG) and Bayer.

Other early-year IPO hopefuls include Tracon Pharmaceuticals, swinging for $47 million; Ascendis Pharma, out to raise $85 million; and Flex Pharma, which is seeking $60 million.

- read Spark's SEC filing

Special Report: FierceBiotech's 2014 Fierce 15 - Spark Therapeutics