Janux Therapeutics Plummets 49%: What's Behind the Bloodbath?

Summary
• Janux Therapeutics (JANX) crashes 49.2% to $17.265, hitting 52-week low of $16.70
• Phase 1 trial update for JANX007 in mCRPC sparks investor exodus
• Options chain shows 102% implied volatility on 12/19 $17.5 put, 84% on 1/16 $15 put

Janux Therapeutics’ stock imploded on Tuesday, collapsing nearly 50% to trade near its 52-week low after the biotech firm released updated Phase 1 data for its prostate cancer candidate JANX007. The sell-off defied the drug’s reported durable responses and manageable safety profile, with analysts debating whether the data overreacted to marginal efficacy metrics. The stock’s intraday range of $16.70–$18.86 underscores extreme volatility, while options traders bet heavily on downside protection and short-term volatility.

Phase 1 Trial Update Sparks Investor Exodus
Janux’s 49% plunge stems from a disconnect between the company’s optimistic framing of its JANX007 Phase 1 data and investor skepticism. While the trial showed 7.9–8.9 months of radiographic progression-free survival (rPFS) in heavily pre-treated mCRPC patients and manageable cytokine release syndrome (CRS), the 30% confirmed/unconfirmed partial response rate in RECIST-evaluable patients fell short of expectations. Analysts highlighted that the data lacked confirmed responses and failed to address concerns about dosing complexity. The stock’s collapse accelerated after William Blair noted the sell-off was an overreaction, but the market’s bearish momentum overwhelmed cautious optimism.

Biotech Sector Mixed as Amgen Gains, Janux Crashes
The broader biotech sector showed mixed signals, with Amgen (AMGN) rising 0.43% as a sector leader. Janux’s 49% drop starkly contrasted with AMGN’s resilience, highlighting sector divergence. While AMGN’s gains reflected confidence in its established pipeline, Janux’s collapse underscored the sector’s risk profile for early-stage biotechs. The disparity suggests investors are prioritizing near-term visibility over speculative clinical-stage bets.

Bearish Options and Short-Term Volatility Playbook
• 200-day MA: $26.85 (well below current price)
• RSI: 75.2 (overbought)
• MACD: 1.88 (bullish divergence)
• Bollinger Bands: $24.24–$34.94 (current price near lower band)

Janux’s technicals suggest a short-term bearish bias despite a long-term ranging pattern. Key support levels at $16.70 (52W low) and $17.50 (strike price of active puts) are critical. The stock’s 75% RSI and MACD histogram above 0.54 indicate overbought conditions and potential reversal. For aggressive traders, the JANX20251219P17.5 put (12/19 expiry, 102% IV, 11.55% leverage) and JANX20260116P15 put (1/16 expiry, 84.82% IV, 18.04% leverage) stand out. The former offers 190.91% price change potential with 0.101 gamma and -0.0609 theta, while the latter provides 47.69% upside with 0.062 gamma and -0.0135 theta. Under a 5% downside scenario (targeting $16.40), the 12/19 $17.5 put would yield $0.90 payoff (K - ST = $17.5 - $16.40), and the 1/16 $15 put would deliver $2.10 (K - ST = $15 - $16.40). These contracts balance liquidity (62,928 turnover for the 12/19 put) and volatility exposure. Aggressive short-term bears may consider JANX20251219P17.5 into a breakdown below $17.50, while longer-term bearish bets could target JANX20260116P15 for a 1/16 expiry play.

Backtest Janux Therapeutics Stock Performance
Below is the interactive event-study dashboard. It summarises how JANX’s share price behaved in the 30 trading-days that followed every occasion (39 occurrences) when the intraday low dropped by ≥ 49 % versus the prior close between 1 Jan 2022 and 2 Dec 2025.How to read it • Each column (1 d, 2 d, … 30 d) shows the cumulative return from the close of the plunge day out to that many trading days after the event, the win-rate (percentage of events with positive return), and statistical significance versus a matching-period benchmark. • Scroll or enlarge the chart area to view the full path of average post-event performance, distribution of returns, and best/worst individual cases.Key take-aways (headline view) 1. Frequency: 39 plunges ≥ 49 % occurred in the sample window. 2. Drift: Median post-event price drift is modest; mean cumulative return reaches ~13 % after 30 days, with no day showing statistical significance at the 95 % level versus the benchmark. 3. Hit ratio: Win-rate gradually improves from c. 49 % on the first day to ~74 % by day 30, but edge remains statistically weak. 4. Risk/Reward: The absence of significance and the heavy downside tails visible in the distribution suggest that simply buying after a -49 % intraday shock has not delivered a reliable edge in this period. Tighter risk controls (e.g. stop-loss) or combining with additional filters may be required.Assumptions & data notes • Event definition: a trading day whose intraday low ≤ 51 % of the prior day’s close (-49 % or worse). • Data source: daily OHLC series retrieved via system API (file janx_daily_ohlc_20220101_20251202.json). • The event-study engine used closing prices and the default 30-day evaluation horizon. • Where parameters were not specified, defaults were applied: price_type=close, backtest window=30 days. Feel free to explore the interactive module above or let me know if you’d like different horizons, risk filters, or further drilling into specific episodes.

Rebound or Reckoning? Watch for $16.70 Breakdown
Janux’s 49% plunge reflects a market overcorrecting to marginal Phase 1 data, but the stock’s technicals and options activity suggest further downside risk. A breakdown below $16.70 (52W low) could trigger panic selling, while a rebound above $18.86 (intraday high) might signal short-covering. Investors should monitor the 12/19 $17.5 put’s liquidity and Amgen’s 0.43% gain as a sector barometer. For now, the path of least resistance is lower, with JANX20251219P17.5 offering a high-leverage, high-gamma play on a potential $16.70 breakdown.