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Stock Watch: Will MacroGenics' SOPHIA Make Heads Turn Again?

MacroGenics Inc. (MGNX) has reported updated results from its phase III study of Margetuximab in patients with HER2-positive metastatic breast cancer who have previously been treated with anti-HER2-targeted therapies.

The study, dubbed SOPHIA, met its first sequential primary endpoint of progression-free survival, noted the Company. The median progression-free survival of patients treated with Margetuximab and chemotherapy was 5.8 months compared to 4.9 months in patients treated with Herceptin (trastuzumab) and chemotherapy.

The objective response rate, a secondary outcome measure in the SOPHIA study, was 22% in the Margetuximab arm compared to 16% in the trastuzumab arm.

Rewind to February 6, 2019... On that day, the Company announced that the SOPHIA clinical trial met the primary endpoint of prolongation of progression-free survival, sending the stock up as much as 190%. Patients in the Margetuximab arm experienced a 24% risk reduction in PFS compared to patients in the trastuzumab arm.

Commenting on the updated results, Scott Koenig, President and CEO of MacroGenics, said, "The activity observed to date in SOPHIA is promising. For overall survival, we anticipate the preliminary positive trend in favor of Margetuximab to continue, although subsequent results could fluctuate as additional events accrue."

At the time of the primary PFS analysis, overall survival data based on 158 events were immature, noted the Company. The median OS at that time was prolonged by 1.7 months in patients treated with Margetuximab and chemotherapy compared to patients treated with trastuzumab and chemotherapy.

The Company anticipates conducting a second pre-specified interim OS analysis based on 270 events in the second half of this year. The final pre-specified OS analysis is planned after 385 events have accrued, and is projected to be completed in 2020.

MacroGenics anticipates submitting a Biologics License Application for Margetuximab to the FDA in the second half of 2019.

MGNX closed Wednesday's trading at $16.27, down 1.57%. In pre-market trading on Thursday, the stock is up over 13% to $18.50.

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