Trio of biosimilars have good showing

Funding Pfizer sponsored the REFLECTIONS trial. Disclosures Dr Socinski disclosed that his institution receives research funding from Pfizer. Source Socinski MA et al. A comparative clinical study of PF-06439535, a candidate bevacizumab biosimilar, and reference bevacizumab, in patients with advanced non-squamous non-small cell lung cancer. ASCO 2018, Abstract 109. https://meetinglibrary.asco.org/record/161702/abstract. Clinical trial registry number NCT02364999 https://clinicaltrials.gov/ct2/show/NCT02364999

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 AEs were essentially the same.

The 48-week results showed a median PFS of 11.1 months with trastuzumab-dkst and 11.1 months with trastuzumab (HR, 0.95; P = .842), reported senior investigator Hope S Rugo, MD, a clinical professor of medicine and director of the Breast Oncology Clinical Trials Program at the University of California, San Francisco, Helen Diller Family Comprehensive Cancer Center. “The overall survival is immature but is impressive at over 80% at 52 weeks,” she noted.

Presence of overall response at 24 weeks correlated with duration of PFS 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 AEs through week 48 were much the same as those seen at week 24, with few additional [events] 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 to a very low number and was identical between the 2 arms. Paclitaxel, which people stayed on for longer [with the biosimilar], may have been the cause of this.”

The 48-week rates of AEs of special interest – respiratory events, cardiac disorders, and infusion-related AEs – and of serious AEs were similar for the 2 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.”

Dr Rugo emphasized that trastuzumab-dkst provides “an additional high-quality treatment option for patients with HER2+ breast cancers in any setting. This study 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.”