Shares of Amgen  (AMGN) where under heavy pressure as last week came to a close. The stock's 1.75% drop on Friday drove it to fresh June lows as downside trade soared. This was quite an ugly reversal from the open that day and has put the stock in a vulnerable position.

If Amgen is unable to hold key support near its April and May lows, the steep slide from the June peak could gain a second wind.

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In late April, Amgen moved into new 2016 high territory after moving past the $160 area. As the powerful rally off the March low extended, Amgen reached major resistance just below $165 before completely running out of momentum. By late April, the stock was in pullback mode, leaving behind a fourth monthly high near $165. The stock fell back below its 200-day moving average as it retraced over 75% of the March through April rally. This deep selloff did considerable damage, and, as shares fell back below the 200 day earlier last week, more damage appears to be ahead.

At the May bottom, Amgen held key support near the April low. Following the late May bounce, the stock is trading just above the $149 area once again. In the near term, Amgen investors should keep a close eye on the $149-to-$147.00 support zone. A clear break through $147 would take out last month's low and would add considerable downside momentum to Friday's high-volume drop. If the May low is broken, Amgen will be on a clear path to a retest of the 2016 lows set back in March. This major support zone, which includes the February low as well, would offer a very low-risk entry opportunity if a fresh base can develop here. Until then, Amgen may prove to be a frustrating long.

Disclosure: This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.