When the warrants are not in the money, they are only a speculation on the future value of the stock;

When they are in the money they have an intrinsic value  - If PTA was 50 cents and the B warrant allowed you to buy the stock at 35 the intrinsic value would be your spread, 15 cents.

Hence the warrant would probably trade around a range of its intrinsic value.  Of course for the same $ invested a warrant will give you leverage / higher rate of return than a stock (and corresponding risk)

For example, a 5 cent gain on a 15 cent warrant to 20 cents would be a ROR of 33% vs. a 5 cent gain on a 50 cent stock which would be 10%.

Hence - Bigger gain potential on Warrants (for the same $ invested) but also bigger risk and in the case of PTA less liquidity.

Best thing to do with them is buy them when they are really cheap and have a longer term to expiry.   Just like anything.