CHICAGO – investigators reported at the annual meeting of the American Society of Clinical Oncology. The findings further advance the promise of new agents that have no clinically meaningful differences in efficacy and safety when compared with their reference drugs but have substantially lower cost.
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Dr. Michael A. Thompson
Bevacizumab biosimilar
The REFLECTIONS trial (NCT02364999) was a multinational, first-line, randomized, controlled trial among 719 patients with advanced nonsquamous NSCLC. Patients were randomized to paclitaxel and carboplatin chemotherapy plus either bevacizumab (sourced from the European Union) or the candidate bevacizumab biosimilar PF-06439535 on a double-blind basis, followed by monotherapy with the same assigned agent.
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Dr. Mark A. Socinski
The confidence interval for the risk difference fell within the equivalence margins set by European Union regulators (–13% and +13% for the 95% confidence interval). And the confidence interval for the risk ratio fell within the equivalence margins set by the Food and Drug Administration (0.73 and 1.37 for the 90% CI) and Japanese regulators (0.729 and 1.371 for the 95% CI).
Median progression-free survival was 9.0 months with the biosimilar and 7.7 months with bevacizumab (hazard ratio, 0.974; P = .814), and corresponding 1-year rates were 30.8% and 29.3%, Dr. Socinski reported. Median overall survival was 18.4 months and 17.8 months (HR, 1.001; P = .991), and corresponding 1-year rates were 66.4% and 68.8%.
Rates of grade 3 or higher hypertension, cardiac disorders, and bleeding did not differ significantly with the two agents. Patients also had similar rates of grade 3 or higher serious adverse events and of fatal (grade 5) serious adverse events (5.3% with the biosimilar and 5.9% with bevacizumab).
“Similarity between PF-06439535 and bevacizumab-EU was demonstrated for the primary efficacy endpoint of overall response rate. ... There were no clinically meaningful differences in safety profile shown in this trial, and similar pharmacokinetic and immunogenicity results were seen across treatment groups,” Dr. Socinski summarized.
“These results confirm similarity demonstrated in earlier analytical, nonclinical, and clinical studies of PF-06439535 with bevacizumab-EU,” he concluded.
Trastuzumab biosimilar
The phase 3 HERITAGE trial was a first-line, randomized, controlled trial that compared biosimilar trastuzumab-dkst (Ogivri) with trastuzumab in combination with taxane chemotherapy and then as maintenance monotherapy in 458 patients with HER2+ advanced breast cancer.
The 24-week results, previously reported (JAMA. 2017 Jan 3;317[1]:37-47), showed a similar overall response rate with each agent when combined with chemotherapy. Rates of various adverse events were essentially the same.
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Dr. Hope S. Rugo
Presence of overall response at 24 weeks correlated with duration of progression-free survival at 48 weeks (biserial r = .752). “Additional patients achieved a response during the monotherapy portion of the treatment, which is intriguing and clearly emphasizes the importance of monotherapy, as well as the importance of having alternate agents at lower cost available,” Dr. Rugo commented.
Common adverse events through week 48 were much the same as those seen at week 24, with few additional ones occurring during monotherapy. “No new safety issues were observed, and in fact, toxicity during monotherapy was quite minor,” she noted. “One thing that’s interesting here is that there was more arthralgia during the first 24 weeks with trastuzumab-dkst than with trastuzumab, but in monotherapy, this fell down to a very low number and was identical between the two arms. Paclitaxel, which people stayed on for longer [with the biosimilar], may have been the cause of this.”
The 48-week rates of adverse events of special interest – respiratory events, cardiac disorders, and infusion-related adverse events – and of serious adverse events were similar for the two agents.
“We didn’t see any additional serious cardiac events during monotherapy,” Dr. Rugo noted. Mean and median left ventricular ejection fraction over 48 weeks were similar, as was the rate of LVEF, which dropped below 50% (4.0% with trastuzumab-dkst and 3.3% with trastuzumab). The incidences of antidrug antibody and neutralizing antibody were also comparably low in both groups.
“HERITAGE data, now at week 48, supports trastuzumab-dkst as a biosimilar to trastuzumab in all approved indications,” Dr. Rugo said. “Final overall survival will be assessed after 36 months or after 240 deaths, whichever occurs first. Based on current data, this is predicted to conclude by the end of 2018, with final overall survival data available next year.
“Trastuzumab-dkst provides an additional high-quality treatment option for patients with HER2+ breast cancers in any setting,” she added. “This study indeed shows that biosimilars offer the potential for worldwide cost savings and improved access to life-saving therapies. It’s sobering to think that the patients enrolled in this study would not otherwise have had access to continued trastuzumab therapy, and so many of them are still alive with longer follow-up.”
