Jefferies analyst David Steinberg downgraded Nektar Therapeutics to Hold from Buy and cut his price target for the shares to $23 from $59. The company last night disclosed a manufacturing issue that resulted in batch to batch variability in certain early lots of bempeg used in clinical testing, Steinberg tells investors in a research note. The analyst believes the disclosure increases uncertainty surrounding Nektar's lead program. While management believes they have a handle on the situation, their hypothesis may not be confirmed for some time, says the analyst.