John Scarlett
Analyst · Ren Benjamin from Rodman
Thanks, Graham. Good afternoon, everyone, and thank you for dialing in to our first quarter call. I'm going to try to keep my comments brief as we provided a relatively thorough business update on our fourth quarter call.
Starting with imetelstat. At the beginning of February, we completed enrollment of our randomized Phase II clinical trial with imetelstat in patients with metastatic breast cancer. This is the first of 2 randomized controlled Phase II studies of imetelstat. We completed enrollment of 166 patients in this trial in just over a year, ahead of our projections. We believe this reflects the need for effective treatments for metastatic breast cancer and was driven by the interest among clinical investigators and patients for compounds with novel mechanisms of action against new targets in metastatic breast cancer, such as telomerase inhibition.
This randomized clinical trial in HER2-negative metastatic breast cancer has been designed to study the effects of imetelstat in combination with paclitaxel chemotherapy. And that treatment will be compared to the progression-free survival of patients treated with paclitaxel alone.
Approximately 1/3 of the patients enrolled in this trial are also receiving Avastin, and the results of the trial will be stratified for the concomitant use of that drug.
Our other randomized Phase II clinical trial with imetelstat is in patients with advanced non-small cell lung cancer. This study has just completed enrollment, and that's new news. It is designed to study the effect of imetelstat in patients receiving the drug as maintenance therapy, following induction chemotherapy with the platinum-based doublet regimen. The comparator arm in this study receives standard of care which, following platinum-based induction chemotherapy, currently is observation and support of care. Patients with non-squamous tumor histology, who received Avastin during induction therapy are continuing to receive Avastin maintenance during the course of this trial in both arms of the study, and we will stratify the results for Avastin treatment.
For both the metastatic breast cancer trial and the non-small cell lung cancer trial, the primary endpoint is progression-free survival, or PFS. Since PFS is event-driven, release of top line data will occur after a pre-specified number of progression events have occurred and the initial analysis of the studies has been completed. Based on our latest analysis of the rate at which events are occurring in both trials, we continue to expect to release top line data for both by the end of this year.
I'd like to shift gears for just a moment and also mention a Geron poster that was presented at the American Association for Cancer Research. And that was at their annual meeting that was recently held in Chicago. And this poster related to predictive diagnostic programs that we're developing in parallel for imetelstat.
Considering the possible mechanism of action of telomerase inhibition in general, and imetelstat in particular, we and others have proposed that tumors with short telomares may be more responsive to treatment with imetelstat. A presentation at the AACR meeting reported that we have developed a proprietary quantitative polymerase chain reaction or QPCR-based assay. And this assay can measure telomare length in tumor samples from patients. Our objective is to use this assay on patient samples from our Phase II clinical trials in both metastatic breast cancer and non-small cell lung cancer in order to look for a correlation between telomare length prior to treatment and clinical outcomes after treatment with imetelstat. If such a positive correlation is observed, in the future it could allow us to enrich clinical trial populations in patients who have tumors with short telomares who would thus presumably be good candidates for imetelstat treatment.
I'd like to move on to an update of our 2 single arm studies of imetelstat in hematologic malignancies, essential thrombocythemia, or ET, and multiple myeloma. These studies are primarily mechanistic studies assessing the effect of imetelstat on the malignant progenitor cells driving these diseases. This is made possible by using assays designed to measure such progenitor cells in samples of peripheral blood or bone marrow taken before and during treatment with imetelstat. With regard to the ET trial, the safety data obtained from using imetelstat in patients with ET in the ongoing study has now enabled us to expand the patient population to include patients with another type of myeloproliferative neoplasm, which is polycythemia vera, known as PV. While ET is characterized by an increase in platelets, the patients with PV primarily have an increase in red blood cells, also driven by malignant hematopoietic progenitor cell in the bone marrow. Patients with PV will start being enrolled in the study pending IRB approval of the amended protocol at our clinical sites.
In this ET NPV study, we are assessing 2 things. First, we're looking for hematologic response, which is a reduction in the number of platelets or red cells in the blood after treatment with imetelstat. However, hematologic response alone will not tell us whether imetelstat has a general effect on the bone marrow or whether the drug can impact the underlying disease by specifically inhibiting the malignant hematopoietic progenitor cells that are responsible for ET or PV. Therefore, we're also looking for a molecular response. Patients with myeloproliferative neoplasms can have certain gene mutations, often the JAK2 gene, which can be detected in circulating blood cells. About 1/2 of the patients with ET and approximately 95% of patients with PV have the JAK2 mutation. We can measure the change and allelic burden of this JAK2 mutation and peripheral blood cells as an indication of disease-modifying drug effect. A molecular response will indicate that imetelstat is specifically inhibiting the malignant progenitor cell. Positive results from this study would allow us to consider further developing imetelstat for myeloproliferative neoplasms, such as myelofibrosis or other hematologic malignancies.
This trial has been slow to enroll because the study requires that patients must have failed or must be intolerant to conventional therapies. Because we're looking specifically at molecular changes, and because those changes would not be expected to occur in the absence of a drug effect, we believe that we'll be able to draw conclusions based on approximately 8 to 10 patients with the JAK2 mutation and expect such data to be available from that number of patients by the end of this year.
The multiple myeloma trial is a small exploratory study in which the number of circulating B-cell myeloma progenitor cells are being measured in the blood and bone marrow, allowing us to estimate the effect of imetelstat on the production of these cells. If a significant reduction is observed after treatment with imetelstat, it would suggest that imetelstat is having a disease-modifying effect on the malignant progenitor cell responsible for the myeloma. As we've reported previously, this study has consistently enrolled behind expectations largely because the study requires patient samples to be handled promptly at the laboratory at Johns Hopkins, where the analysis is done. We have therefore recently opened a second site at the University of Maryland where patient enrollment has begun. We plan to complete enrollment, review and report preliminary data for approximately 6 to 10 patients by year end, which we believe will give us sufficient data to evaluate whether or not imetelstat is having its intended effect on the malignant myeloma clone.
If that is suggested by the study results, it may encourage us to plan a trial in one or more hematologic malignancies using imetelstat.
Finally, I'd like to end with an update on our second clinical stage product candidate, GRN1005. 1005 is a novel peptide drug conjugate designed to utilize a physiologic molecular transport mechanism, known as LRP-1, to deliver paclitaxel across the blood-brain barrier where it can treat brain metastases. As we've reported previously, Phase I data in solid tumor brain metastases showed encouraging single agent activity. Patients receiving 1005 had a 20% overall response rate using measurements of both intracranial and extracranial disease. Approximately 24% of patients with brain metastases had a greater than 30% shrinkage in brain lesions, and 50% of patients with lung lesions had a greater than 30% shrinkage in those lesions. These data strongly suggest that GRN1005 has activity against cancers inside and outside of the brain compartment, both of which can cause death in patients who have brain mass.
In the fourth quarter of 2011, we initiated 2 1005 clinical trials, one in patients with brain metastases from non-small cell lung cancer, and a second trial in patients with brain metastases from breast cancer. The non-small cell lung cancer trial was a single-agent, single-arm study that evaluates overall response rate, which includes both intracranial and extracranial disease as a primary endpoint. The breast cancer trial is also a single-arm study, which includes 2 cohorts: Patients with HER2-positive and HER2-negative disease. Each of these cohorts has 50 patients. The patients with HER2-positive disease will also be treated with Herceptin. The primary endpoint for the metastatic breast cancer trial is intracranial response rate. Although both of these trials have just begun enrollment, investigator interest in our early patient enrollment appears strong, and we continue to expect top line data by the end of the second quarter of 2013.
So that covers the clinical program updates. I'd like to end by noting that, during the first quarter, we announced the appointment of Dr. Bryan Lawlis, an expert in drug manufacturing, to our board. Dr. Lawlis was previously the Vice President of Process Science at Genentech and the CEO of Aradigm, a publicly-traded biotech company, and is currently also on the boards of Biomarin Pharmaceutical and Sutro Biopharma. In the first quarter, we also announced the appointments of Graham Cooper as CFO and Executive Vice President of Finance and Business Development; and Steven Rosenfield as Executive Vice President, General Counsel and Corporate Secretary.
That concludes my prepared remarks. Thank you for your attention, and your interest in the company. Operator, we'd be happy to take questions now.