It's an insurance policy. Nothing more. It'll cost a small amount of capital to secure the right to raise money in the future, if it's needed.
I don't see what the big deal is. But for the sake of argument let's suppose that Dr. Missling taps into his 200mm authorized share limit and forces LPC to purchase the full $150mm worth of shares, at say $10/share. Anavex would then have $290mm in cash, no debt, and just over 100mm shares outstanding.
What's so bad about that situation? This is a non-issue. LPC funding was much scarier when the stock traded under $2.