Rib-X Files for $80M IPO as Lead Antibiotic Nears Phase III
By Trista Morrison
With Phase IIb data for antibiotic delafloxacin expected by the end of the year and a Phase III trial slated to start in 2012, Rib-X Pharmaceuticals Inc. moved to bolster its balance sheet by raising up to $80 million in an initial public offering.
Rib-X joins eight other biotechs currently waiting in the IPO wings: Argos Therapeutics Inc., Cempra Holdings LLC, ChemoCentryx Inc., Insys Therapeutics Inc., Merrimack Pharmaceuticals Inc., Supernus Pharmaceuticals Inc., TVAX Biomedical Inc. and Verastem Inc. All of them filed within the last 12 months, and six of the filings came since July – indicating that either confidence or desperation is on the rise.
Data for the year as a whole point to the latter. The biotech IPO class of 2011 is trading down about 8 percent, and all except Clovis Oncology Inc. priced below their intended ranges. Yet confidence could have the edge if fall trends count for anything. The November pricings of Clovis and NewLink Genetics Corp. have managed to stay above water in the aftermarket, and Clovis' $130 million take was the biggest of the year. (See BioWorld Today, Nov. 17, 2011.)
For Rib-X, an IPO would provide much-needed cash to advance the firm's clinical pipeline, including the fluoroquinolone antibiotic delafloxacin and the oxazolidinone antibiotic radezolid, as well as a handful of preclinical and discovery-stage compounds.
Prior to 2007, Rib-X raised $122.4 million in three venture rounds to support its programs. When it closed its Series C round in 2006, the company told BioWorld Today it hoped the money would carry it through an IPO by the end of 2007. (See BioWorld Today, Jan. 4, 2002, May 2, 2003, and June 21, 2006.)
But as the markets took a turn for the worse and the IPO window slammed shut, Rib-X was forced to fund its operations primarily through a series of smaller convertible debt financings, and as of Sept. 30, the biotech had just $9.7 million in cash, equivalents and marketable securities. Although Rib-X snagged a potentially lucrative partnership with Sanofi SA this summer for preclinical antibiotic program RX-04, the deal was back-end loaded and provided just $10 million up front plus a $9 million research milestone. (See BioWorld Today, July 7, 2011.)
Rib-X reported about $30 million in operating expenses for the first nine months of 2011 , so an $80 million IPO should give the New Haven, Conn.-based firm a couple of years of runway.
A good chunk of the funding would likely go toward Phase III trials of the broad-spectrum fluoroquinolone antibiotic delafloxacin. Those trials are expected to begin in the second half of 2012, assuming all goes well with the ongoing Phase IIb trial in acute bacterial skin and skin structure infections (ABSSSI), which should read out by the end of the year.
A previous Phase II trial in skin infections showed an 88 percent clinical response rate with the 300-mg twice-daily dose of I.V. delafloxacin, compared to 82 percent for Tygacil (tigecycline, Pfizer Inc.). A separate Phase II trial in community-acquired pneumonia (CAP) showed an 87 percent clinical response rate at both the 200-mg and 400-mg oral delafloxacin doses.
Another hefty chunk of Rib-X's IPO proceeds would likely go to the biotech's other clinical candidate, the I.V. and oral oxazolidinone antibiotic radezolid.
A Phase II trial in uncomplicated skin and skin structure infections showed an 82 percent clinical response rate with 450 mg radezolid once daily vs. 83 percent for Zyvox (linezolid, Pfizer Inc.).
A separate Phase II trial in CAP showed an 80 percent cure rate at the same dose.
Rib-X's drugs will go up against an increasing number of new antibiotics seeking differentiation based on higher cure rates, better tolerability, less resistance, activity against MRSA and I.V. to oral dosing strategies.
Fellow IPO hopeful Cempra is gearing up for pivotal trials with CEM-101 , a macrolide antibiotic designed for high potency, high barriers to resistance, and both I.V. and oral dosing, as well as Taksta, an oral dosing regimen of fusidic acid that has shown comparable safety and efficacy to Zyvox. (See BioWorld Today, Oct. 14, 2011.)
Meanwhile Trius Therapeutics Inc. is in Phase III with tedizolid phosphate, an oxazolidinone antibiotic designed to be more potent, better tolerated and less vulnerable to resistance than Zyvox, while also offering strong activity against MRSA and both oral and I.V. dosing.
Rib-X's earlier stage programs focus on targeting newly discovered antibacterial and antifungal binding sites within ribosomes.
Terms for Rib-X's proposed IPO have not yet been disclosed. Underwriters include Deutsche Bank Securities, William Blair & Co., Lazard Capital Markets and Needham & Co. LLC. Rib-X plans to list its shares on the Nasdaq Global Market under the symbol "RIBX."
In the U.S. and Canada: 1-800-336-4474
Outside the U.S.: 1-215-386-0100
Hours: Monday - Thursday, 8:30 am - 6:00 pm EST
Friday, 8:30am - 4:30 pm EST
Sign up for Perspectives FREE e-mail newsletter