Immunomedics results bolster case for efficacy in aggressive breast cancer
- A paper in the Journal of Clinical Oncology confirms that Immunomedics' lead antibody-drug conjugate (ADC), sacituzumab govitecan (IMMU-132), is active in patients with metastatic triple-negative breast cancer (TNBC) who have failed a series of other treatments.
- In the 69 patients reported on in the paper, the objective response rate (ORR) was 30%, including two complete remissions and 19 partial responses, which the authors point out is a higher ORR than expected.
- This was a group of patients who had tried a number of different therapies — despite this, almost 70% had a reduction in tumor burden that began early on in treatment, and median progression-free survival was 6 months, almost twice the predicted 3.5 months with standard care.
The IMMU-132 data provides a "couple of new nuggets", according to analysts at Jefferies, though they point out that the "data are a bit dated", as the paper reports on 69 patients with a cutoff date of August 2016, and there are now 85 assessable patients. This time lag is understandable because of the publication cycle of journals.
"IMMU-132 continues to produce meaningful clinical benefit in metastatic triple-negative breast cancer patients who are exhausting standard treatment options," remarked Cynthia Sullivan, president and CEO of Immunomedics. "We are working diligently with the FDA to make this valuable product candidate available to this group of patients as soon as possible. Blinded, independent radiological assessments are ongoing, and so far show a high concordance with local tomography findings."
The checkpoint inhibitors are an exciting development in cancer treatment, but inevitably, some patients will fail on immuno-therapies due to their effectiveness in only small patient populations so far. One of the interesting points in this study is the observation that of the four patients who had failed checkpoint inhibitor treatment, three showed a partial response to IMMU-132, which may suggest potential for sequential or combination therapy approaches, as the two drug types do not seem to exhibit cross-resistance.
IMMU-132 targets the glycoprotein Trop-2, and the study also looked at using Trop-2 staining as a possible biomarker. Those patients who responded to the drug seemed to show stronger Trop-2 staining. While the results are still early, the authors say that as a predictive biomarker, Trop-2 warrants further research.
Immunomedics has had a tumultuous time of late, with activist investor VenBio Select Advisors wresting control of the board and dropping in its four nominees. Current CEO Cynthia Sullivan announced in January that she would be stepping down when the company files for accelerated approval of IMMU-132 to the Food and Drug Administration, expected in mid-2017.
There is still no news on the status of the Seattle Genetics deal for the drug, which is dependent on a court decision.
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