progress that our colleagues at Five Prime have achieved, both for shareholders and, most importantly, for patients. We expect this deal to close by the end of the second quarter, and is subject to customary closing conditions, including the tender of at least a majority of the outstanding shares of Five Prime’s common stock and the expiration or termination of the waiting period under the Hart-Scott-Rodino Act. Finally, I would like to reaffirm our full year financial outlook that we shared with you last month on our fourth quarter call, with revenue guidance for 2021 of $25.8 billion to $26.6 billion and non-GAAP earnings per share guidance of $16 to $17 per share. I would now like to turn the call over to our Head of Research and Development, Dave Reese, who will talk about the molecule, the unmet need that we can potentially address and the recently disclosed Phase II data, which looks promising. Dave?
David M. Reese - Amgen Inc. - EVP of Research & Development
Thanks, Peter, and hello, everyone. Thank you again all for joining us on short notice this morning. As Peter said, we’re thrilled by today’s announcement and believe this is a strong strategic fit. Five Prime is an innovative clinical stage biotechnology company focused on developing immuno-oncology and targeted cancer therapies for patients with solid tumors. And this is strongly aligned with our own immuno-oncology and precision medicine strategy.
First and foremost, bemarituzumab or bema has the potential to address a very significant global unmet medical need. Gastric cancer is the third most common cause of cancer death worldwide, with over 1 million new cases diagnosed annually. And in Asia, in particular, gastric cancer is a significant public health challenge. For context, annually, there are nearly as many cases of gastric cancer in China, Japan and Korea as there are all major solid tumors in the United States.
As we previously discussed, we have 2 clinical programs from our BiTE platform targeting proteins also highly expressed in gastric cancer, AMG 199, targeting MUC17, and AMG 910, which targets CLDN 18.2. The bema program very nicely complements these efforts and adds to our internal expertise.
So let’s talk a little bit about - more about bemarituzumab, the lead asset. This is a fibroblast growth factor receptor 2b or FGFR2b monoclonal antibody advancing into Phase III development as a potential front line therapy for gastric and gastroesophageal junction, or GEJ, cancer patients, whose tumors overexpress the receptor.
For those who aren’t familiar with this receptor signaling pathway, I’d like to give you just a little bit of background biology so that you can put things into context. FGFR2B is a splice variant of fibroblast growth factor receptor 2, which is itself a member of a broad and complex FGFR family. A variety of oncogenic alterations can occur in FGFRs, including point mutations, fusions, translocations, gene amplification or receptor overexpression.
In the case of FGFR IIb specifically, which is what we’re talking about here, over-expression is most common in gastric cancer and occurs in approximately 30% of tumors based on the extensive screening data Five Prime generated in the context of the Phase II FIGHT study. Bemarituzumab is an afucosylated antibody, and it exerts its antitumor effects by inhibiting ligand binding to the FGFR2b receptor as well as through enhanced antibody-dependent cell-mediated cytotoxicity. Specifically, bemarituzumab inhibits the ligand binding of FGF7, 10 and 22, thus avoiding some of the metabolic complications, such as hyperphosphatemia, that can occur with perturbation of FGF23, one of the many ligands that can bind to receptors in this family.
Our interest, of course, like many experts in gastric cancer, was peaked by the clinical data Five Prime has generated to date, which we believe are compelling. In early phase trials, proof-of-concept was demonstrated with single-agent activity in late-line gastric cancer with an overall confirmed response rate of 18%. For context, this is roughly comparable to single-agent Herceptin activity in advanced HER2-positive breast cancer or the activity of Vectibix alone in colorectal cancer.