Posts Tagged → pancreatic cancer
In my last post on The Haystack, we discussed the phase III data from the Abraxane MPACT trial in advanced pancreatic cancer that was presented at the recent ASCO GI meeting in San Francisco. Two other late-stage studies in pancreatic cancer caught my eye—fresh data for AB Science’s kinase inhibitor masitinib and Sanofi’s multidrug pill S1.
Masitinib is an oral tyrosine kinase inhibitor from AB Science that targets KIT, PDGFR, FGFR3 and has shown activity in gastrointestinal stromal tumours (GIST). A different version of the drug (Masivet, Kinavet) is also approved in France and the US for the treatment of a dog mast cell (skin) cancers, which are also known to be KIT-driven.
S1 is multidrug pill from Sanofi and Taiho that consists of tegafur (a prodrug of 5FU), gimeracil (5-chloro-2,4 dihydropyridine, CDHP) which inhibits dihydropyrimidine dehydrogenase (DPD) enzyme, and oteracil (potassium oxonate, Oxo), which reduces gastrointestinal toxicity. Previous Japanese studies have demonstrated effectiveness of this agent in gastric and colorectal cancers, so a big unaswered question is whether it is effective in pancreatic cancer.
So what was interesting about the latest data at this meeting?
At the ASCO GI conference in 2009, French oncologist Emmanuel Mitry presented data from a small Phase II study of the effect of combining masitinib and Eli Lilly’s Gemzar in advanced pancreatic cancer. The study had just 22 patients, but the median overall survival of 7.1 months in was not a large improvement over what is often seen with the standard of care, Gemzar given alone, or with a combination of Gemzar and Genentech’s Tarceva. Over the years, many combination therapies based on Gemzar have failed to show superiority over single agent therapy. It’s both a high unmet medical need and a high barrier to beat. Thus, the phase III data for the combination of masitnib and Gemzar was highly anticipated at this year’s ASCO GI meeting.
Gael Deplanque and colleagues compared masitinib plus Gemzar to Gemzar plus placebo. Although the overall trial results for median overall survival were slightly higher than in the phase II study, they were not significant (7.7 versus 7.0 months, P=0.74; HR=0.90).
Some promising data was observed, however, in a subset of the population identified by a profile of biomarkers that the authors vaguely described as, “a specific deleterious genomic biomarker (GBM) consisting of a limited number of genes.” No other details on the actual genes or biomarkers were was provided, but the subset was described as having an improved MOS to 11.0 months compared to the Gemzar and placebo arm.
They also noted that patients with high pain, who usually do poorly on standard chemotherapy, also saw improvement with the masitinib combination. AB Science might have found a particularly aggressive subset that respond to masitinib, in which case, a biomarker would be useful in selecting those patients most likely to respond, as opposed to a catch-all approach where everyone is treated regardless of the predictive value.
AB Science has asked European regulatory authorities for approval, but the Phase III data will not be sufficient for US approval. The company will need to validate the biomarker panel in a large-scale randomized study, and a new phase III trial is now recruiting patients. The outcome of that study won’t be known for awhile, but the hope is for more insight into how to choose the right patients to respond to masitinib in combination with Gemzar.
The other compound featuring late-stage results in pancreatic cancer was Sanofi’s S1. The compound is interesting, but so far its development has been limited to Asian patients, particularly people of Japanese origin. Studies in caucasians have not seen any benefit over standard 5FU therapy.
Katsuhiko Uesaka, medical deputy director at Shizuoka Cancer Center Hospital in Japan, presented encouraging data for the use of S1 as adjuvant therapy in combination with Gemzar after surgical resection (relevant in stage I-III pancreatic cancer). They compared S1 and Gemzar in a head to head non-inferiority trial (with 385 patients. In the interim analysis reported at this year’s ASCO GI meeting, the hazard ratio for S-1 to Gemzar was 0.56, while the 2-year survival rates were 53% for Gemzar and 70% for S-1. The percentage of serious side effects were similar to previously reported studies with Gemzar and S-1, including fatigue (4.7/5.4), anorexia (5.8/8.0), leukopenia (38.7/8.6), thrombocytopenia (9.4/4.3), anemia (17.3/13.4), and elevated AST (5.2/1.1).
Overall, the authors concluded that S-1 adjuvant chemotherapy was shown to be as good as, perhaps even better than Gemzar, even suggesting that S-1 could be considered the new standard treatment for resected pancreatic cancer. It should be noted, however, that this data is only applicable to patients of Japanese origin since no caucasian data was included in this analysis.
The cancer research conference season kicked off in earnest in 2013 with the American Society of Clinical Oncology (ASCO)’s Gastrointestinal Symposium, held in San Francisco in late January. Some of the most anticipated data to be presented at ASCO GI was for drugs that treat pancreatic cancer, with three drugs—Celgene’s Abraxane, AB Science’s masitinib, and Sanofi’s S1, generating the most interest.
With this post, we’ll take a closer look at the most advanced of the three agents, Abraxane, which generated encouraging results in a Phase III study. Later this week, we’ll tackle masitinib and S1.
Abraxane is a nanoparticle albumin-bound form of the breast cancer drug paclitaxel, and is designed to improve the activity of the active ingredient. Abraxane is already approved in the US for advanced breast and lung cancers, and recently showed signs of activity in metastatic melanoma.
At ASCO GI, Daniel Von Hoff, director of the Translational Genomics Research Institute, presented data from a randomized phase III study called MPACT that compared the effects of Lilly’s Gemzar, the current standard of care, to a once weekly combination of Gemzar and Abraxane in patients with metastatic adenocarcinoma of the pancreas. With 861 patients, this was a large global study that sought to determine whether the combination would outdo the regulatory standard of care.
A note on the trial design: Although this study uses Gemzar as the standard of care, in practice, many leading oncologists prescribe FOLFIRINOX (fluorouracil, leucovorin, irinotecan and oxaliplatin) for advanced pancreatic patients. But because FOLFIRINOX is generic, and is not formally approved by FDA for advanced pancreatic cancer, Phase III studies tend to match new drug candidates up against Gemzar.
As Hedy Kindler, director of gastrointestinal oncology at the University of Chicago, explained, FOLFIRINOX is widely used because the regimen has “the higher response rate, and that has the longer median survival.”
However, FOLFIRINOX also has unpleasant side effects, and in private practice settings, oncologists prefer to use less toxic combinations based on Gemzar—namely, Gemzar alone, GemOx (with oxaliplatin), or GemErlotinib (with Tarceva, an EGFR TKI). To provide context, FOLFIRINOX typically has an improved survival of approximately 11 months, while gemcitabine or gemcitabine plus erlotinib elicit a 6-7 month improvement in median overall survival (MOS). Erlotinib added 12 days of extra survival over gemcitabine alone, but unfortunately we have no way of selecting those advanced pancreatic patients most likely to respond to EGFR therapy.
Celgene is exploring the combination of Abraxane and Gemzar based on preclinical work that suggests Abraxane can knock out the protective stroma surrounding the tumor, thereby providing better penetration of the tumor. The phase II data led to a promising 12.2 months improvement in median overall survival.
In general, results from randomized phase III trials tends to be lower than that reported in the smaller studies. This is exactly what happened in the MPACT trial, with the Abraxane combination showing a MOS of 8.7 months versus 6.7 months for Gemzar alone, a highly statistical significant finding (P<0.000015). The hazard ratio (HR) was 0.72, suggesting that the combination gave a 28% reduction in the risk of death versus gemcitabine.
Kindler is eager to use and learn more about the combination and notes that it will be another option for oncologists rather than a new standard of care.
This is encouraging data and met the primary endpoint. Celgene is expected to file for approval for Abraxane in advanced pancreatic adenocarcinoma in the second half of the year. Data on a previously identified biomarker (SPARC expression) was not yet available and is expected to be presented at the annual ASCO meeting in June. The audience at the GI meeting were clearly expecting survival to be higher in those patients with high SPARC expression, but we will see what happens.
Advanced pancreatic cancer is a particularly devastating disease – the incidence and prevalence are approximately equal, with patients typically having a year of life left. The symptoms are vague and insidious plus there are no useful screening approaches approved for earlier detection, so the emergence of potential biomarkers for selecting patients most likely to respond to Abraxane or Tarceva in combination with gemcitabine would be a most welcome advance, especially given the toxicities associated with FOLFIRINOX.