Health care stocks fell hard on Monday, including a nearly 2.4% decline for the NYSE Health Care Index while shares of health care companies in the S&P 500 also were down nearly 2.2% as a group. The Nasdaq Biotechnology index was dropped slightly more than 2.3%.

Among health care stocks moving on news:

(+) Sellas Life Sciences Group (SLS) shares were 1.5% higher this afternoon, drifting off a nearly 6% gain that followed the company saying has completed enrollment in phase II trial of its nelipepimut-S drug candidate in women with a form of breast cancer where their milk ducts have become cancerous. Initial data from this trial are expected by the end of this year, Sellas said.

In other sector news:

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(+) Allakos (ALLK) more than doubled in price on Monday, at last look rising 111%, after the biotechnology company said its AK002 drug candidate met its primary endpoint during phase II testing, producing a 95% reduction of gastrointestinal tissue in patients with eosinophilic gastritis or gastroenteritis compared with a 10% reduction in patients treated with a placebo. It also reported a narrower-than-expected loss.

(+) Heron Therapeutics (HRTX) was slightly higher Monday afternoon. The specialty drugmaker saw its Q2 net loss widen to $0.63 per share from $0.54 per share during the same quarter last year but still beating the Capital IQ consensus expecting a $0.64 per share net loss. Net product sales rose 112% year over year to $36.6 million, also exceeding the $31.4 million Street view.

(-) Henry Schein (HSIC) was 2% lower after the medical products distributor Monday said it has acquired a majority stake in Cliniclands, a Swedish distributor serving dental practices throughout Scandinavia and generating around $9.5 million in yearly sales. Terms of the transaction were not disclosed.