Oppenheimer analyst Carlos Solorzano says FDA issued a complete response letter, or CRL, for AstraZeneca's (AZN) ZS-9, citing issues observed during a pre-approval manufacturing inspection and receipt of recently-submitted data. The analyst continues to believe ZS-9 will get approved and that there would be some black-box warning in the label surrounding the edema rates observed. However, this setback for ZS-9 will likely give Relypsa's (RLYP) Veltassa an "even better" lead in the market, Solorzano tells investors in a research note. He reiterates an Outperform rating and $36 price target on Relypsa's shares.

Bearish flow noted in AstraZeneca with 3,362 puts trading, or 1.7x expected. Most active are 4/26 weekly 70 puts and May-24 70 calls, with total volume in those strikes near 3,600 contracts. The Put/Call Ratio is 1.72, while ATM IV is up nearly 2 points on the day. Earnings are expected on April 25th.