Buy the calls and short the stock. You'll make $$$ on the upside and downside - if it just languishes @ current levels then you'll lose $$$ due to decay (theta) of the option premium - I havent looked at the options in a while so I'm not sure how expensive or cheap implied vol is, but if its relatively low (for MNTA) then it might be worth a shot - if you are somewhat more bullish then you might adjust your short hedge down a little rather then keeping the trade delta neutral.
But likely those go to zero (or close to it) if Teva got approval. So hard for me to see how that is a conservative strategy.
Buying calls makes little sense to me here. There is unlikely to be an explosive move to the upside (chances are better for a slow and steady increase over a long period), whereas there could be to the downside.
Selling just out of the money covered calls is a better strategy in my view. So still bullish (you are net long), but the premium gives you more income and/or some protection on the downside.