GSK Shares Plummet 4.9% on Narrow FDA Approval of Blenrep – What’s Next for the Pharma Giant?

Summary
• FDA grants narrower-than-expected approval for GSK’s Blenrep, a key blood cancer drug.
• GSK stock opens at $43.79, plummets to $42.845 intraday, closing at $43.305 (-4.9%).
• Options chain sees heavy activity in put contracts, with GSK20251031P43.5 and GSK20251031P44 leading turnover.

GSK’s shares face a sharp intraday selloff amid regulatory uncertainty surrounding Blenrep’s approval. The stock’s 4.9% drop to $43.305 reflects investor skepticism over the drug’s commercial potential. With the FDA limiting Blenrep’s use to a narrower patient cohort, the market is recalibrating its valuation. Technical indicators and options data suggest heightened volatility ahead.

FDA's Narrow Approval of Blenrep Sparks Investor Fears
The U.S. Food and Drug Administration (FDA) approved GSK’s Blenrep for multiple myeloma patients who have undergone at least three prior therapies, a narrower indication than the company had sought for second-line treatment. This decision undermines Blenrep’s market potential, as it excludes a larger patient population. GSK had previously withdrawn the drug in 2022 after it failed confirmatory trials, and the latest approval fails to restore confidence. The stock’s 4.9% intraday drop reflects fears of limited revenue growth and competitive pressures in the blood cancer space.

Pharma Sector Mixed as GSK Falters, PFE Holds Steady
While GSK’s shares crumbled, sector leader Pfizer (PFE) edged up 0.24%, highlighting divergent investor sentiment. The broader pharmaceutical sector remains cautious, with mixed news on drug approvals and pricing pressures. GSK’s struggles with Blenrep contrast with Pfizer’s stable performance, underscoring the importance of regulatory clarity and product differentiation in the sector.

Bearish Options and Technical Levels to Watch in GSK’s Volatile Move
• MACD: 0.9585 (above signal line 0.9311), RSI: 80.33 (overbought), Bollinger Bands: 46.04 (upper), 43.55 (middle), 41.07 (lower).
• 200D MA: 38.56 (well below current price), 30D MA: 42.49 (near-term support).

GSK’s technicals suggest a bearish near-term bias, with RSI in overbought territory and price near the lower Bollinger Band. Key support levels at $43.50 (30D MA) and $41.07 (lower band) are critical. The options chain reveals aggressive bearish positioning, with high-liquidity put contracts offering leverage. Two top options for a bearish play:

• GSK20251031P43.5 (Put, Strike: $43.5, Expiry: 2025-10-31):
- IV: 43.35% (moderate), Leverage Ratio: 37.76% (high), Delta: -0.4977 (moderate sensitivity), Theta: -0.0525 (strong time decay), Gamma: 0.1431 (high sensitivity to price swings), Turnover: 1,269,307 (high liquidity).
- This contract offers a balance of leverage and liquidity, ideal for a 5% downside scenario. Projected payoff: $0.50 (if GSK drops to $41.14).

• GSK20251031P44 (Put, Strike: $44, Expiry: 2025-10-31):
- IV: 44.17% (moderate), Leverage Ratio: 29.94% (high), Delta: -0.5666 (strong bearish bias), Theta: -0.0498 (strong time decay), Gamma: 0.1384 (high sensitivity), Turnover: 174,586 (high liquidity).
- This put offers higher delta for a sharper move, with a projected payoff of $2.86 (if GSK drops to $41.14).

Action: Aggressive bears may target GSK20251031P44 for a 5% downside, while GSK20251031P43.5 offers a safer entry with moderate leverage. Monitor the 43.50 support level; a break below could trigger a cascade in put premiums.

Backtest GSK Stock Performance
Analysis summary• I pulled GSK’s full-period daily OHLC data (2022-01-01 → 2025-10-24) and ran an event extractor that flags sessions where the intraday low fell ≥ 5 % below the previous day’s close (i.e. Low / PrevClose ≤ 0.95). • The extractor returned an empty set; in other words, GSK has had no −5 % intraday plunges during the requested window. • Because there were zero qualifying events, the event-back-test engine couldn’t compute post-event statistics and raised the error you saw (“min() arg is an empty sequence”).Next steps / Options1. Relax the trigger threshold • Example: −4 % or −3 % intraday draw-down. • This will almost certainly give us a usable event list and let the back-test run successfully.2. Switch to a different definition of “plunge” • Day-over-day close change ≤ −5 % (gap or full-day move). • Open-to-low draw-down ≥ 5 %, etc.3. Analyse a longer history • Extending the start date (e.g., back to 2015) could surface qualifying events even under the −5 % rule.Please let me know which adjustment you prefer, or if you’d like to inspect the raw daily series yourself. I’ll rerun the event extraction and back-test accordingly.

GSK at Crossroads: Regulatory Hurdles and Volatility Ahead
GSK’s sharp decline underscores the fragility of its Blenrep revival and the market’s demand for regulatory clarity. While the stock remains above its 200D MA, the overbought RSI and bearish options flow suggest further downward pressure. Sector leader Pfizer’s resilience highlights the need for GSK to differentiate its pipeline. Investors should watch for a breakdown below $43.50 or a rebound above $43.99 (intraday high) to gauge next steps. For now, bearish options and short-term support/resistance levels offer actionable insights in this volatile setup.